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Is Bilingual Education Desirable in Multilingual countries?

  • Kazuhiro Yuki ORCID logo EMAIL logo
Published/Copyright: October 12, 2022

Abstract

In many countries, people use their mother tongue in local business, but use the language of the former colonizer in national business. How much weight should be placed on teaching one’s mother tongue and the lingua franca is a critical issue in these countries. This paper develops a model to examine these issues theoretically. It is shown that balanced education of the two languages is critical for skill development of those with limited wealth. It is also found that balanced bilingual education yields higher earnings net of educational expenditure than lingua-franca-only education only when a country has favorable educational and technological conditions (productivity is reasonably high and education is reasonably effective) and only for those with adequate wealth. Policy implications of the results are also discussed.

JEL Classification: I25; J24; O15; Z13

Corresponding author: Kazuhiro Yuki, Faculty of Economics, Kyoto University, Yoshida-hommachi, Sakyo-ku, Kyoto 606-8501, Japan, E-mail:

Award Identifier / Grant number: 10197395

Acknowledgment

Invaluable comments from an anonymous referee and helpful comments from participants at the 2017 Asian Meeting of the Econometric Society are gratefully acknowledged.

  1. Research funding: Financial support from JSPS through Grants-in-Aid for Scientific Research 10197395 is acknowledged. Data sharing is not applicable to this paper as no new data were created or analyzed in this study.

  2. Conflict of interest statement: The author declares no conflicts of interest regarding this article.

  3. Author contributions: The author has accepted responsibility for the entire content of this submitted manuscript and approved submission.

Appendix A: Analysis of the Effect of sl on Earnings When e+<ē

This appendix examines in detail the effect of sl on earnings when e+<ē.

A.1 When the Return to Education for Local Jobs is Constrained to be Positive

First, as in Section 4.2, the effect is examined under the assumption that the return to educational investment for local jobs is positive for any sl. The next proposition summarizes analytical results, based onProposition A1 in Appendix B, which presents a fully detailed statement. This proposition is the counterpart of Proposition 3 when e+=ē. In the proposition, symbol e+(sl) is used to signify the dependence of e+ on sl (e+′(sl) > 0 from Lemma 1).

Proposition 5

Suppose that the return to education for local jobs is positive and e+<ē holds.

    1. If the proportion of those with limited wealth is high enough that e+(0)α1αh̲lδl holds, d(wnhn)dsl<0 for any sl.

    2. Otherwise, d(wnhn)dsl>(<)0 for small (large) sl. sl maximizing wnhn is smaller than sl, the critical sl when e+=ē.

    1. If ē1+α1αh̲lδl, d(wlhl)dsl>(<)0 for small (large) s l when a(= e) is large, while d(wlhl)dsl<0 for any sl when a(=e) is small. In the former case, sl maximizing wlhl is greater than sl(e), the critical sl when e+=ē.

    2. Otherwise, d(wlhl)dsl is negative for small sl, positive for middle sl, and negative for large sl when a(=e) is intermediate, while when it is small and large, results are similar to (a). In the former case, sl maximizing (minimizing) wlhl is greater (smaller) than sl(e)(sl°(e)), the critical sl when e+=ē.

    3. The maximum a(=e) such that d(wlhl)dsl<0 holds for any sl is lower than when e+=ē.

As shown in Proposition A1 in Appendix B, unlike the case e+=ē, analytical results cannot be obtained for some ranges of sl and as for wlhl, a(=e). However, the above proposition and numerical simulations suggest that results for workers with a local job are qualitatively the same as the case e+=ē: when ē1+α1αh̲lδl, wlhl increases (decreases) with sl for small (large) sl when a(=e) is large, and wlhl decreases with sl for any sl when it is small; when ē>1+α1αh̲lδl, wlhl decreases with sl for small sl, increases with sl for middle sl, and decreases with sl for large sl when a(=e) is intermediate, while the results when it is large and small are similar to the previous case. As for the relationship between s l maximizing wlhl and a(=e), unlike the case e+=ē, an analytical result is not obtained but numerical simulations suggest that the relationship is positive as before.

There exist minor differences from the case e+=ē. First, sl maximizing earnings of workers with a local job and a above the threshold is greater than sl(e), the critical sl when e+=ē. Second, the maximum level of a(=e) such that the earnings decrease with sl for any sl (and thus sl = 0 maximizes the earnings) is lower than when e+=ē. From Proposition 1, for given sl, e+<(=)ē holds when F(ē) is relatively large (small). Hence, these results suggest that individuals choosing a local job are more likely to benefit from the education of the skill useful in their future jobs when the share of those who face the wealth constraint on educational investment, including themselves, is high, i.e. e+<ē, than when the share of such individuals is low, i.e. e+=ē.

Results for workers with a national job are also similar to the case e+=ē, but some differences exist. First, if the proportion of those with limited wealth is high enough that e+(0)α1αh̲lδl, wnhn decreases with sl for any sl. Numerical simulations suggest that wlhl of those who actually choose a local job (i.e. those with ae+(sl)) also decreases with sl in this case. These results indicate that earnings of all workers decrease with sl when a large proportion of people have limited wealth for education. Second, when e+(0)>α1αh̲lδl, sl maximizing wnhn is smaller than sl when e+=ē. Hence, in contrast to workers with a local job, workers who have abundant wealth to choose a national job are less likely to benefit from the education of the skill for local jobs when e+<ē than when e+=ē.

A.2 When the Return to Education for Local Jobs is Endogenous

Now, as in Section 5, the effects of sl on earnings net of educational spending is examined by taking into account the fact that whether the return to education for local jobs is positive or not is endogenously determined, drawing on Propositions 1 and 2 as well as Proposition 5. The following proposition is the counterpart of Proposition 4 when e+=ē. Note that unlike when e+=ē, the proposition does not cover intermediate ranges of A, δn, δl, and a and as for (iii) of the proposition, some ranges of sl. In what follows, sl̲(f) (sl̄(f)) denotes the lower (higher) sl such that the return to education for local jobs is 0 when e+<ē. (“f” is to indicate the dependence of their values on the distribution of wealth.) Appendix B provides a fully detailed statement of the proposition.

Proposition 6

Suppose that e+<ē holds.

  1. When A, δn, or δl is small, net earnings of all workers decrease with sl except at sl=sl̲(f), sl=sl̄(f), or both, where they increase discontinuously.[35] The net earnings are maximized at sl = 0 if A, δn, or δl is sufficiently small.

  2. Those with wealth below a certain level choose a local job for any sl. Their net earnings decrease with sl except at sl=sl̄(f), where they increase discontinuously, and are maximized at sl = 0.

  3. When A, δn, and δl are not small, net earnings of those with wealth greater than a certain level decrease with sl for small sl, increase with sl for middle sl, and decrease with sl for large sl. When δ l is sufficiently large, their net earnings are maximized at sl(sl̲(f),sl̄(f)).[36]

The first part of the proposition shows that, if A, δn, or δl is small, net earnings of everyone decrease with sl except at either sl=sl̲(f), sl=sl̄(f), or both, where, differently from the case e+=ē, they increase discontinuously. But, as before, net earnings are highest at sl = 0 if A, δn, or δl is sufficiently small. The second part shows that irrespective of values of A, δn, and δl, net earnings of those with little wealth decrease with sl except at sl=sl̄(f), where, unlike when e+=ē, the earnings increase discontinuously, but as before, are highest at sl = 0. The last part shows that, when A and δn are not small and δl is sufficiently large, net earnings of those with sufficient wealth are highest at sl(sl̲(f),sl̄(f)).

Appendix B: More Precise Statements for Several Propositions and a Claim

This appendix presents more precise statements for Proposition 1 in Section 3.3, Proposition 4 in Section 5, and Propositions 5 and 6 in Appendix A. The appendix also presents Claim 1 that is used for drawing Figure 3 in Section 2.

Proposition 1

Suppose that A is not extremely low so that wlδlsl1=(1α)×Aαδn(1sl)e+(1α)h̲l+δlsle+αδlsl1>0 at sl satisfying h̲l(1slαsl)h̲lF(e+)+1slαδlsl0e+ef(e)de+1α(1slαsl)h̲l+(1slα)slδle+hl(e+,sl)×e+f(e+)=0 when e+<ē.[37] Then,

    1. There exist two critical values of sl ∈ (0, 1) at which the return to educational investment for local jobs equals 0, and for sl smaller (greater) than the lower (higher) critical value, the return is negative and individuals with wealth a < e+ do not spend on education, while the return is positive and they spend e = a on education for s l between the critical values.

    2. The lower [higher] critical value of sl decreases [increases] with A, δn and δl.

  1. When sl is small or large enough that the return to educational investment for local jobs is negative, e+<(=)ē holds iff F(ē) is large (small) enough that F(ē)(1α)F(ē)α1F(ē)1αAδn(1sl)αh̲lē1α>()1. When the return is positive, e+<(=)ē holds iff F(ē)>()1αh̲l+δlsl0ēef(e)deh̲l+δlsl(1α)ē. When F(ē)1α, e+=ē always holds.

Proposition 4

Suppose that F(ē)1α and thus e+=ē hold.

  1. If A, δn, or δl is small enough that sl̲>sl, net earnings of all workers decrease with sl.[38]

  2. Otherwise,

    1. Net earnings of workers with a national job decrease with sl for sl<sl̲, increase with sl for sl(sl̲,sl), and decrease with sl for sl>sl. The net earnings are maximized at sl=sl when A, δn, and δl are large enough that (1α)2α21αα1+h̲lδlēδl1α>F(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]ē1α.[39]

    2. Net earnings of workers with a local job and wealth above a certain level decrease with sl for sl<max{sl̲,sl°(e)}, increase with sl for sl(max{sl̲,sl°(e)},sl(e)), and decrease with sl for sl>sl(e), while net earnings of workers with wealth below the threshold decrease with sl for any sl. The threshold equals e satisfying sl(e)=sl̲ if ē1+α1αh̲lδl and if ē>1+α1αh̲lδl and slΛ(ē)sl̲, where Λ(ē)αh̲lδl+ē1+δl4h̲ē(1α)ē(1+α)h̲lδl2, otherwise, it equals Λ(ē). Net earnings of the former workers with wealth a = e are maximized at sl=sl(e), when A, δn, and δl are large enough that Aδnēα(1α)α(1sl(e))1ααh̲l+δlsl(e)ē1ααF(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]1α+ēe>0.

    3. sl̲ in (a), max{sl̲,sl°(e)} and the threshold wealth in (b) decrease with A, δn, and δl.

Proposition 6

Suppose that e+<ē holds.

  1. When A, δn, or δl is small enough that either e+(0)α1αh̲lδl or sl̲(f)sl(sl satisfies sl=(1α)αh̲lδle+(sl)) and sl̲(f)sl,h(e) hold,[40] net earnings of all workers decrease with sl except at sl=sl̲(f), sl=sl̄(f), or both, where they increase discontinuously.[41] The net earnings are maximized at sl = 0 if A, δn, or δl is small enough that 1ααh̲lδne+(0)1α>(1α)2Aδl1ααα.

  2. Those with wealth below a certain level choose a local job for any sl. The threshold wealth equals mine+(0),αh̲lδl+E(e|e<e+(0)) when E(e|e<e+(0))1+α1αh̲lδl and equals mine+(0),Ω(e+(0)) when E(e|e<e+(0))>1+α1αh̲lδl, where Ω(e+(0))αh̲lδl+E(e|e<e+(0))1+δl4h̲lE(e|e<e+(0))(1α)E(e|e<e+(0))(1+α)h̲lδl2. Their net earnings decrease with sl except at sl=sl̄(f), where they increase discontinuously, and are maximized at sl = 0.

  3. When A, δn, and δl are large enough that e+(0)>α1αh̲lδl, E(e|e<e+(0))>αmax11αh̲lδl,e+(0)1+α, and min{sl,sl,h(e)}>sl̲(f)(sl satisfies sl=(1α)αh̲lδlE(e|e<e+(sl))), net earnings of those with wealth greater than maxαh̲lδl+e+(0),Λ(ē) decrease with sl for small sl, increase with sl for middle sl, and decrease with sl for large sl.[42] When δl is large enough that h̲le+(0)1α<h̲l+δlslēē1α(1sl)α for those with a national job and (1α)Aδnα1αα{(αe)α[h̲l+δl(1α)e]1α e+(0)α(h̲l)1α}e>0 for those with a local job and wealth a = e, their net earnings are maximized at sl(sl̲(f),sl̄(f)).[43],[44]

The following proposition presents more precise results for Proposition 5. Note that except (i)(a) of the proposition, conditions are sufficient but not necessary. Proofs of the proposition and the claim below are contained in Appendix D posted on the author’s webpage (http://www.econ.kyoto-u.ac.jp/yuki/english.html).

Proposition A1

Suppose that the return to education for local jobs is positive and e+<ē holds.

    1. If e+(0)α1αh̲lδl, which is true when the proportion of individuals with limited wealth is high, d(wnhn)dsl<0 for any sl.

    2. Otherwise, d(wnhn)dsl<0 for slsl, where sl(0,sl) satisfies sl=(1α)αh̲lδle+(sl), and when E(e|e<e+(0))0e+(0)ef(e)deF(e+(0))>maxα1αh̲lδl,αe+(0)1+α, d(wnhn)dsl>0 for slsl, where sl(0,sl) satisfies sl=(1α)αh̲lδlE(e|e<e+(sl)).

    1. If ē1+α1αh̲lδl, d(wlhl)dsl>0 for slsl,h(e)(sl(e),sl,h(e)) when e>maxαh̲lδl+e+(0),Λ(ē), d(wlhl)dsl<0 for slsl,h(e) when e>maxαh̲lδl+E(e|e<e+(0)),Ω(ē)(Ω(ē)<Λ(ē)), and d(wlhl)dsl<0 for any sl when eαh̲lδl+E(e|e<e+(0)), where sl,h(e) is the greater solution of L(sl)ee+(sl)sl2+(1α)e+(sl)(1+α)h̲lδlesl+αh̲lδl+e+(sl)+eh̲lδl=0 and Λ(ē)αh̲lδl+ē1+δl4h̲lē(1α)ē(1+α)h̲lδl2, while sl,h(e) is the greater solution of M(sl) = 0, where M(sl) equals L(s l ) with e+(sl) replaced with E(e|e < e+(sl)), and Ω(ē) equals Λ(ē) with ē replaced with E(e|e<ē).

    2. Otherwise, d(wlhl)dsl>0 for slmax{0,sl,l(e)},sl,h(e) when e>maxαh̲lδl+e+(0),Λ(ē),[45] d(wlhl)dsl<0 for slmax{0,sl,l(e)} and slsl,h(e) when emaxαh̲lδl+E(e|e<e+(0)),Ω(ē),[46] and d(wlhl)dsl<0 for any sl when e ≤ Ω(e+(0)) and when E(e|e<e+(0))1+α1αh̲lδl and eαh̲lδl+E(e|e<e+(0)), where sl,l(e)(sl,l(e)) is the smaller solution of L(sl) = 0 (M(sl) = 0).

Claim 1

Suppose 0ēef(e)de(0,(1α)ē]. As illustrated in Figure 3, on the (sl,F(ē)) plane, the dividing line between e+<ē and e+=ē when the return to educational investment for local jobs is positive is located below the dividing line when the return is negative on the loci for zero return.

Appendix C: Proofs of Lemmas and Propositions

Proof of Proposition 1

    1. Suppose that education is worthwhile for local jobs. Consider case e+<ē first. From (2)(4) and (7), the marginal return to education for local jobs when e+<ē equals

(14)wlδlsl1=(1α)Aαhne+,sl(1α)hle+,slαδlsl1=(1α)Aαδn(1sl)e+(1α)h̲l+δlsle+αδlsl1.

In the above equation,

(15)dδn(1sl)e+h̲l+δlsle+dsl=h̲l+δlsle+δne++δn(1sl)de+dslδn(1sl)e+δle++δlslde+dslh̲l+δlsle+2=h̲l+δle+δne++h̲lδn(1sl)de+dslh̲l+δlsle+2,

where the numerator equals, from (37) in the Proof of Lemma 1 below,

(16)h̲l+δle+δne++h̲lδn(1sl)de+dsl=h̲l+δle+δne++h̲lδn(1sl)δle+(1α)e+ēef(e)de+[1F(ē)]ēα0e+ef(e)de(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)=δne+h̲l+δle+(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)+δl(1sl)h̲l(1α)e+ēef(e)de+[1F(ē)]ēα0e+ef(e)de(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)=δne+hle+,sl(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+h̲l+δle+hle+,sle+f(e+)+δl(1sl)h̲lα0e+ef(e)de(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)<0.

The sign of the derivative of wlδlsl − 1 with respect to sl is same as the sign of the following derivative, which, by using the above equations, can be expressed as

(17)dδn(1sl)e+h̲l+δlsle+(sl)1αdsl=dδn(1sl)e+h̲l+δlsle+dsl(sl)1α+δn(1sl)e+h̲l+δlsle+1α(sl)1αsl=(sl)1αδne+h̲l+δlsle+hle+,sl(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+h̲l+δle+e+f(e+)+δl(1sl)h̲lα0e+ef(e)de(h̲l+δlsle+)(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)+1α1slsl=(sl)1αhle+,sl2δne+hle+,sl(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+h̲l+δle+e+f(e+)+δl(1sl)h̲lα0e+ef(e)de1α1slslhle+,sl(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)=(sl)1αδne+hle+,sl2hle+,sl1slαslαsl(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+1slαslαslh̲l+1slααδle+e+f(e+)δl(1sl)h̲lα0e+ef(e)de(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)

Since (1α)e+ēef(e)de+1F(ē)ēhl(e+,sl)=α0e+(h̲l+δlsle)×f(e)dee+ from (7), (5), (3), and (4), the numerator of the above equation becomes (sl)1αδne+ times

(18)1slαslslh̲l0e+(h̲l+δlsle)f(e)de+1slαslαslh̲l+1slααδle+hle+,sle+×f(e+)δl(1sl)h̲lα0e+ef(e)de=1slh̲l(1slαsl)h̲lF(e+)+1slαδlsl0e+ef(e)de+1α(1slαsl)h̲l+(1slα)slδle+hle+,sle+f(e+).

The following lemma presents the critical result on (18).

Lemma A1

There exists an sl(1α,11+α) such that (18) equals zero and the equation is positive (negative) for lower (higher) sl.

Proof of Lemma A1

Clearly, (18) is positive for sl ≤ 1 − α and negative for sl11+α. (18) is positive for sl greater than 1 − α and weakly lower than the unique sl(1α,11+α) satisfying (1slαsl)h̲l+(1slα)slδle+=0 too, because, for such sl, (1slαsl)h̲l+(1slα)slδle+0 and (1slαsl)h̲lF(e+)+1slαδlsl0e+ef(e)de1slαδlsle+F(e+)0e+ef(e)de>0, where the former statement is true from

(19)d(1slαsl)h̲l+(1slα)slδle+dsl=(1+α)h̲l+(12slα)δle++(1slα)δlslde+dsl<(1+α)h̲l+(12slα)δle+<0 for sl>1αsince de+dsl>0.

Thus, the lemma is proved if the derivative of the expression inside the curly bracket of (18) with respect to sl is negative for sl greater than the critical value and lower than 11+α, which equals

(20)h̲ld(1slαsl)h̲lF(e+)+1slαδlsl0e+ef(e)dedsl+1αd(1slαsl)h̲l+(1slα)slδle+dslhle+,sle+f(e+)+1α(1slαsl)h̲l+(1slα)slδle+dhle+,sle+f(e+)dsl,
(21)where  d(1slαsl)h̲lF(e+)+1slαδlsl0e+ef(e)dedsl=(1+α)h̲lF(e+)+(12slα)δl0e+ef(e)de+(1slαsl)h̲l+(1slα)slδle+f(e+)de+dsl<(1+α)h̲lF(e+)+(12slα)δl0e+ef(e)de<0for sl greater than the critical value,

where the first inequality sign is from (19). Hence, the derivative of (18) is negative if the last term of (20) is negative, which holds unless f′(e+) is negative and f(e+) is very large, since (1slαsl)h̲l+(1slα)slδle+<0 for such sl. □

From the lemma, there exists an sl(1α,11+α) such that the derivative of the marginal return wlδlsl − 1 with respect to sl equals zero, and the marginal return increases (decreases) with sl for sl smaller (greater) than the critical value. Because the marginal return equals −1 at sl = 0, 1 from (14), if A is high enough that wlδlsl − 1 > 0 holds at sl such that (18) equals zero, there exist two critical values of sl satisfying wlδlsl − 1 = 0 and the marginal return is negative for sl smaller than the lower critical value and greater than the higher one and positive for sl between them. Next, consider case e+=ē. In this case, from (8)(10),

(22)Hl(ē,πn,sl)=(1α)1F(ē)hl(ē,sl)+0ēhl(e,sl)f(e)de,Hn(ē,πn,sl)=α1F(ē)hl(ē,sl)+0ēhl(e,sl)f(e)dehn(ē,sl)hl(ē,sl).

Thus, from (2)(4), the marginal return when e+=ē equals

(23)wlδlsl1=(1α)Aαhn(ē,sl)(1α)hl(ē,sl)αδlsl1=(1α)Aαδn(1sl)ē(sl)1α(1α)h̲l+δlslēαδl1.

In the above equation,

(24)dδn(1sl)ēh̲l+δlslē(sl)1αdsl=dδn(1sl)ēh̲l+δlslēdsl(sl)1α+δn(1sl)ēh̲l+δlslē(sl)1ααsl=(sl)1αδnēh̲l+δlslēh̲l+δlē+h̲l+δlslē1slαslh̲l+δlslē=(sl)1αδnē1αslh̲l+δlslē(1slαsl)h̲l+δlēsl(1slα)h̲l+δlslē,

which is positive (negative) for sl smaller (greater) than the critical value satisfying (1slαsl)h̲l+δlēsl(1slα)=0. Hence, the statement is true as in the case of e+<ē. (b) The result when e+=ē is straightforward from (23). When e+<ē, the marginal return depends on e+ from (14), thus how these exogenous variables affect the return through e+ must be examined. From (7), (5), (3), and (4), e+ is a solution to

(25)α0e+h̲l+δlslef(e)dee+=(1α)e+ēef(e)de+1F(ē)ēh̲l+δlsle+.

Thus, e+ does not depend on A and δn and the result on these variables is straightforward from (14). e+ depends positively on δl from (35) in the Proof of Lemma 1 and the derivative of the RHS − LHS of the above equation with respect to δl, which equals

(26)(1α)e+ēef(e)de+1F(ē)ēsle+α0e+slef(e)dee+=αsle+0e+h̲l+δlslef(e)dee+h̲l+δlsle+0e+ef(e)de>0.

The result on δl is clear from (14) and de+dδl>0. (ii) When the return to education for local jobs is positive, e+=ē iff (10) satisfies πn ≤ 1, i.e.

(27)α0ēhl(e,sl)f(e)de(1α)[1F(ē)]hl(ē,sl)α0ēh̲l+δlslef(e)de(1α)[1F(ē)]h̲l+δlslēh̲lF(ē)+δlslα0ēef(e)de+(1α)ēF(ē)(1α)h̲l+δlslēF(ē)(1α)h̲l+δlslēδlslα0ēef(e)deh̲l+δlsl(1α)ē=1αh̲l+δlsl0ēef(e)deh̲l+δlsl(1α)ē.

When 0ēef(e)de>(1α)ē, which implies F(ē)>1α, e+=ē cannot hold, because the RHS of (27) decreases with sl and is smaller than 1 − α. When 0ēef(e)de(1α)ē, the RHS weakly increases with sl, hence e+=ē could hold and e+=ē always when F(ē)1α. The rest of the statement is straightforward from (27) (note that F(ē) raises 0ēef(e)de and lowers the RHS). When the return is negative, from (12), (4), and (13), wnhn(ē,sl)ē=wlh̲l is expressed as

(28)αAF(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]hn(ē,sl)1αδn(1sl)1ē=(1α)Aπn[1F(ē)]hn(ē,sl)F(ē)+(1πn)1F(ē)h̲lαh̲l.
πn ∈ (0, 1] satisfying the above equation exists, that is, e+=ē holds iff the LHS of the above equation is weakly smaller than the RHS at πn = 1:
(29)αAF(ē)h̲l[1F(ē)]hn(ē,sl)1αδn(1sl)1ē(1α)A[1F(ē)]hn(ē,sl)F(ē)h̲lαh̲lαAF(ē)h̲l[1F(ē)]ē1αδn(1sl)αē(1α)A[1F(ē)]ēF(ē)h̲lαh̲lδn(1sl)αA[1F(ē)]ēF(ē)h̲lαh̲l[1F(ē)]ēF(ē)(1α)F(ē)(1α)F(ē)α1F(ē)1αAδn(1sl)αh̲lē1α1.

Clearly, the condition is satisfied when F(ē)1α. It holds when F(ē) is low because the derivative of the first part of the LHS of (29) with respect to F(ē) equals

(30)F(ē)α1F(ē)1αf(ē)1F(ē)(1α)αF(ē)1α1F(ē)F(ē)α1F(ē)1α2=F(ē)α1F(ē)1αf(ē)1F(ē)(1α)αF(ē)F(ē)1F(ē)F(ē)α1F(ē)1α2=F(ē)α1F(ē)1αf(ē)α(1α)F(ē)α1F(ē)1α3>0.

Proof of Lemma 1

[When the return to educational investment for local jobs is positive]. When e+<ē, by totally differentiating (7), one obtains

(31)αHle+,slhne+,sle+(1α)Hne+,slhle+,sle++αHle+,sle+hne+,sl(1α)Hne+,sle+hle+,slde++αHle+,slhne+,slsl(1α)Hne+,slhle+,slsl+αHle+,slslhne+,sl(1α)Hne+,slslhle+,sldsl=0,
(32)whereHle+,sle+=hle+,slf(e+)>0,Hne+,sle+=hne+,slf(e+)<0.
(33)Hle+,slsl=0e+hl(e,sl)slf(e)de=δl0e+ef(e)de>0.
(34)Hne+,slsl=e+ēhn(e,sl)slf(e)de+[1F(ē)]hn(ē,sl)sl=δne+ēef(e)de+[1F(ē)]ē<0.

In (31), the term of de+ equals

(35)αHle+,slhne+,sle+(1α)Hne+,slhle+,sle++hne+,slhle+,slf(e+)=1e+αHle+,slhne+,sl(1α)Hne+,slhle+,slh̲l+hne+,slhle+,slf(e+)=1e+(1α)Hne+,slh̲l+hne+,slhle+,slf(e+)(from(7))=δn(1sl)(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+e+hle+,slf(e+)>0,

The terms of dsl equals (δδnδl)

(36)αHle+,slhne+,slsl(1α)Hne+,slhle+,slsl+αhne+,sl0e+hl(e,sl)sl×f(e)de(1α)e+ēhn(e,sl)slf(e)de+[1F(ē)]hn(ē,sl)slhle+,sl=δle+αHle+,slδ+(1α)Hne+,sl+αhne+,sl0e+ef(e)de+(1α)δe+ēef(e)de+[1F(ē)]ēhle+,sl=δle+(1α)Hne+,slhne+,slδhle+,sl+hne+,sl+αhse+,sl0e+ef(e)de+(1α)δe+ēef(e)de+[1F(ē)]ēhle+,sl(from(7))=δl(1α)e+ēef(e)de+[1F(ē)]ēδhle+,sl+hne+,sl+αhse+,sl0e+ef(e)de+(1α)δe+ēef(e)de+[1F(ē)]ēhle+,sl(from(5)and(4))=δlhne+,sl(1α)e+ēef(e)de+[1F(ē)]ēα0e+ef(e)de<0,

where the last inequality holds because

αh̲l0e+f(e)de+δlsl0e+ef(e)dee+=(1α)e+ēef(e)de+[1F(ē)]ē×h̲l+slδle+
αF(e+)e+(1α)e+ēef(e)de+[1F(ē)]ēh̲l=slδle+(1α)e+ēef(e)de+[1F(ē)]ēα0e+ef(e)de from(7)and thus sign(1α)e+ēef(e)de+[1F(ē)]ēα0e+ef(e)de=signαF(e+)e+(1α)e+ēef(e)de+[1F(ē)]ē.

Hence,

(37)de+dsl=δlhne+,sl(1α)e+ēef(e)de+[1F(ē)]ēα0e+ef(e)de1e+(1α)Hne+,slh̲l+hne+,slhle+,slf(e+)=δle+(1α)e+ēef(e)de+[1F(ē)]ēα0e+ef(e)de(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)>0.

When e+=ē, from (10),

(38)dπndsl=αhl(ē,sl)0ēhl(e,sl)slf(e)dehl(ē,sl)sl0ēhl(e,sl)f(e)de[1F(ē)]hl(ē,sl)2=αδlh̲l0ēef(e)deē0ēf(e)de[1F(ē)]hl(ē,sl)2<0.

[When the return is negative] First consider case e+<ē. From (12), (4), and (11), wnhne+,sle+=wlh̲l can be expressed as

(39)αAF(e+)h̲le+ēef(e)de+1F(ē)ēδn(1sl)1αδn(1sl)1e+=(1α)Ae+ēef(e)de+1F(ē)ēδn(1sl)F(e+)h̲lαh̲lαAF(e+)h̲le+ēef(e)de+1F(ē)ē1αδn(1sl)αe+=(1α)Ae+ēef(e)de+1F(ē)ēF(e+)h̲lαh̲l

Since the LHS increases with e+, the RHS decreases with e+, and the LHS decreases with sl, e+ satisfying the above equation increases with s l . When e+=ē, from (12), (4), and (13), wnhn(ē,sl)ē=wlh̲l can be expressed as

(40)αAF(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]ē1αδn(1sl)1ē=(1α)Aπn[1F(ē)]ēF(ē)+(1πn)1F(ē)h̲lαh̲lαAF(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]ē1αδn(1sl)αē=(1α)Aπn[1F(ē)]ēF(ē)+(1πn)1F(ē)h̲lαh̲l.

Since the LHS decreases with πn, the RHS increases with πn, and the LHS decreases with sl, πn satisfying the above equation decreases with sl. □

Proof of Lemma 2

[When the return to educational investment for local jobs is positive]. When e+<ē, from (2) and (32) in the Proof of Lemma 1,

(41)wne+=(1α)wn1Hle+,slHle+,sle+1Hne+,slHne+,sle+=(1α)wnf(e+)hle+,slHle+,sl+hne+,slHne+,sl=wnf(e+)hne+,slHne+,sl(from (7))=wne+e+ēef(e)de+[1F(ē)]ēf(e+)>0.

From (2), (33), and (34) in the Proof of Lemma 1,

(42)wnsl=(1α)wn1Hle+,slHle+,slsl1Hne+,slHne+,slsl=(1α)δlwn1Hle+,sl0e+ef(e)de+δHne+,sle+ēef(e)de+[1F(ē)]ē=(1α)δlwn0e+ef(e)deh̲l0e+f(e)de+δlsl0e+ef(e)de+1δl(1sl)=(1α)δlwnh̲lδl0e+f(e)de+0e+ef(e)de(1sl)h̲l0e+f(e)de+δlsl0e+ef(e)de=wne+e+ēef(e)de+[1F(ē)]ēαh̲l0e+f(e)de+δl0e+ef(e)de(1sl)hle+,sl>0.

The last equality is because αh̲l0e+f(e)de+δlsl0e+ef(e)dee+=(1α)e+ēef(e)de+[1F(ē)]ēhle+,sl from (7). From (41), (42), and (37) in the Proof of Lemma 1,

(43)dwndsl=wnsl+wne+de+dsl=wne+e+ēef(e)de+[1F(ē)]ēαh̲lF(e+)+δl0e+ef(e)de(1sl)hle+,sl+δlf(e+)e+(1α)e+ēef(e)de+[1F(ē)]ēα0e+ef(e)de(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)=wne+e+ēef(e)de+[1F(ē)]ē×αh̲lF(e+)+δl0e+ef(e)de(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)+(1sl)hle+,slδlf(e+)e+(1α)e+ēef(e)de+[1F(ē)]ēα0e+ef(e)de(1sl)hle+,sl(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)=wne+e+ēef(e)de+[1F(ē)]ē×αh̲lF(e+)+δl0e+ef(e)de(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)δl(1sl)(1α)e+ēef(e)de+[1F(ē)]ē+αh̲lF(e+)+δlsl0e+ef(e)de(1sl)hle+,sl(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)=wnhle+,sle+11sl(1α)αh̲le+h̲lF(e+)+δl0e+ef(e)de+h̲le++δlhle+,sle+f(e+)(1α)h̲le+e+ēef(e)de+[1F(ē)]ē+hle+,sle+f(e+)>0,

where the last equality is again from (7). When e+=ē, from (8)(10),

(44)Hl(πn,sl)=0ēhl(e,sl)f(e)de+1α1+0ēhl(e,sl)f(e)de[1F(ē)]hl(ē,sl)1F(ē)hl(ē,sl)=(1α)0ēhl(e,sl)f(e)de+1F(ē)hl(ē,sl),
(45)Hn(πn,sl)=αhn(ē,sl)hl(ē,sl)0ēhl(e,sl)f(e)de+1F(ē)hl(ē,sl).

By substituting the above equations into (2),

(46)wn=αA1ααhl(ē,sl)hn(ē,sl)1α.

Thus,

(47)dwndsl=(1α)wn1hl(ē,sl)δlē+1hn(ē,sl)δnē=(1α)wn11slhl(ē,sl)+δlδnhn(ē,sl)hl(ē,sl)>0.

Since wl=(1α)AHnHlα=(1α)AαAwnα1α from (2), dwldsl=α1αwlwndwndsl<0. [When the return is negative] Straightforward from Lemma 1 and the first equation of (39) when e+<ē and of (40) when e+=ē. □

Proof of Proposition 2

When e+<ē, wlh̲l=wnhne+,sle+=wnhn(1,sl)1e+ decreases with sl from Lemma 2. Then, wnhn(e,sl)e=wnhn(1,sl)1e for e > e+ also decreases with sl, because wnhn(1, sl) − 1 decreases with sl from the above equation and de+dsl>0 (Lemma 1). When e+=ē, wlh̲l=wnhn(ē,sl)ē decreases with sl from Lemma 2. □

Proof of Proposition 3

  1. From (47) in the Proof of Lemma 2,

(48)d[wnhn(ē,sl)]dsl=dwndslhn(ē,sl)+wndhn(ē,sl)dsl=wnhn(ē,sl)1sl(1α)hl(ē,sl)+δlδnhn(ē,sl)hl(ē,sl)1=wnhn(ē,sl)1sl(1α)δlδnhn(ē,sl)αhl(ē,sl)hl(ē,sl).

Thus,

(49)d(wnhn)dsl0(1α)δl(1sl)ēαh̲l+δlslē0sl(1α)αh̲lδlē.
  1. From (47) in the Proof of Lemma 2 and (2),

(50)d[wlhl(e,sl)]dsl=dwldslhl(e,sl)+wldhl(e,sl)dsl=α1αwlwndwndslhl(e,sl)+wldhl(e,sl)dsl=wl1sl1hl(ē,sl)αhl(ē,sl)+δlδnhn(ē,sl)hl(e,sl)+δle(1sl)hl(ē,sl).

Thus,

(51)d(wlhl)dsl0αh̲l+δlēh̲l+δlsle+δle(1sl)h̲l+δlslē0eē(sl)2+(1α)ē(1+α)h̲lδlesl+αh̲lδl+ē+eh̲lδl0.
  1. Suppose that the LHS of (51) is positive at sl = 0, i.e. e>αh̲lδl+ē. Because the derivative of the LHS at sl = 0 is non-positive, i.e. (1α)ē(1+α)h̲lδl0 and the LHS at sl = 1 equals eē+(1α)ē(1+α)h̲lδle+αh̲lδl+ē+eh̲lδl=αh̲lδl+ēh̲lδl+e<0, there exists an sl(e)(0,1) such that d(wlhl)dsl0slsl(e), where sl(e)>0, since, from (51),

(52)sl(e)=(1α)ē(1+α)h̲lδle+(1α)ē(1+α)h̲lδl2e2+4eēαh̲lδl+ē+eh̲lδl2eē=(1α)ē(1+α)h̲lδl+(1α)ē(1+α)h̲lδl2+4ēαh̲lδl+ēe1+1h̲lδl2ē.
sl(e)<sl for e<ē, since wlhl(ē,sl)=wnhn(ē,sl) (thus sl(ē)=sl) and sl(e)>0. Suppose instead that the LHS of (51) is non-positive at sl = 0, i.e. eαh̲lδl+ē. Because the derivative of the LHS at sl = 0 is non-positive and the LHS at sl = 1 is negative, d(wlhl)dsl<0 for any sl > 0 (and d(wlhl)dsl<(=)0 at sl = 0 when e<(=)αh̲lδl+ē). (b) The case in which the LHS of (51) at sl = 0 is positive, i.e. e>αh̲lδl+ē, can be proven as in (a). Suppose that the LHS at sl = 0 is zero, i.e. e=αh̲lδl+ē. Since the derivative of the LHS at sl = 0 is positive, i.e. (1α)δlē(1+α)h̲l>0, there exists an sl(e) in (0, 1) such that the LHS of (51) equals 0, and the LHS is zero at sl = 0, positive for sl0,sl(e), and negative for sl>sl(e). Thus, d(wlhl)dsl0 for positive slsl(e) and d(wlhl)dsl=0 at sl = 0. Instead, suppose that the LHS of (51) at sl = 0 is negative, e<αh̲lδl+ē. Since the derivative of the LHS at sl = 0 is positive, i.e. (1α)δlē(1+α)h̲l>0, the LHS is positive (negative) when e>(<)αh̲lδl+ēh̲lδlēsl+(1α)ē(1+α)h̲lδlsl+h̲lδl, where αh̲lδl+ēh̲lδlēsl+(1α)ē(1+α)h̲lδlsl+h̲lδl<αh̲lδl+ē when sl > 0 and ēsl+(1α)ē(1+α)h̲lδl>0sl(0,(1α)(1+α)h̲lδlē). So the LHS of (51) is negative for any e<αh̲lδl+ē when sl(1α)(1+α)h̲lδlē. For sl<(1α)(1+α)h̲lδlē, the LHS of (51) is positive (negative) when e>(<)αh̲lδl+ēh̲lδlēsl+(1α)ē(1+α)h̲lδlsl+h̲lδl, where the RHS is lowest when ēsl+(1α)ē(1+α)h̲lδlēsl=0sl=(1α)ē(1+α)h̲lδl2ē. Hence, the LHS of (51) is negative, i.e. d(wlhl)dsl<0, for any sl when eαh̲lδl+ēh̲lδlēsl+(1α)ē(1+α)h̲lδlsl+h̲lδl at sl=(1α)ē(1+α)h̲lδl2ē=αh̲lδl+ēh̲lδlh̲lδl+(1α)ē(1+α)h̲lδl24ē=αh̲lδl+ē1+δl4h̲ē(1α)ē(1+α)h̲lδl2, except at sl=(1α)ē(1+α)h̲lδl2ē and e=αh̲lδl+ē1+δl4h̲ē(1α)ē(1+α)h̲lδl2, in which the derivative is zero. When eαh̲lδl+ē1+δl4h̲ē(1α)ē(1+α)h̲lδl2,αh̲lδl+ē, there exist sl°(e) and sl(e), where 0<sl°(e)<sl(e)<(1α)(1+α)h̲lδlē<sl, such that the LHS of (51) equals 0, and the LHS is negative for sl < sl°(e) and sl>sl(e) and positive for slsl°(e),sl(e). sl(e)>0>sl(e) from (52). □

Proof of Proposition 4

e+=ē always holds when F(ē)1α from Proposition 1 (ii). The following lemma is used in the proof of the proposition.

Lemma A2

When e+=ē, net earnings change continuously when the return to educational investment for local jobs turns from negative to positive with a change in sl.

Proof of Lemma A2

When e+=ē and the return is negative, wnhn(ē,sl)ē=wlhl(0,sl)αAHlHn1αδn(1sl)1ē=(1α)AHnHlαh̲l, where Hl=F(ē)+(1πn)1F(ē)h̲l and Hn=πn[1F(ē)]hn(ē,sl), from (13) and (12). When e+=ē and the return is positive, wnhn(ē,sl)ē=wlhl(ē,sl)ēαAHlHn1αδn(1sl)1ē=(1α)AHnHlαh̲l+δlslēē, where Hl=0ēhl(e,sl)f(e)de+(1πn)1F(ē)hl(ē,sl) and Hn=πn[1F(ē)]hn(ē,sl), from (2), (8), and (9). When the return is zero, i.e. wlδlsl − 1 = 0, this equation becomes αAHlHn1αδn(1sl)1ē=(1α)AHnHlαh̲l, the same equation as the case of the negative return, and net earnings of all workers are the same. Since HnHl satisfying this equation is uniquely determined for given sl, net earnings when the return is zero are same as net earnings when the return is negative and slsl̲, sl̄. □

(i) Earnings decrease with sl when the return to education for local jobs is negative from Proposition 2, while when it is positive and e+=ē, earnings of all decrease with sl for sl>sl(1α)αh̲lδlē from Proposition 3. From Proposition 1 (i)(b), the lower critical value for the negative return, sl̲, decreases with A, δl, and δn. Hence, from Lemma A2, net earnings of all decrease with sl when A, δl, and δn are small enough that sl̲sl=sl(e+)=sl(ē)(1α)αhlδlē. Note that sl is smaller than the higher critical value sl̄, since sl<1α<sl̄ from Lemma A1 in the Proof of Proposition 1.

(ii) (a) When sl̲<sl=sl(e+)=sl(ē), from Propositions 2 and 3 and Lemma A2, net earnings of workers with a national job decrease with sl for sl<sl̲, increase with sl for sl(sl̲,sl), and decrease with sl for sl>sl. Thus, their net earnings are maximized at either sl = 0 or sl=sl. From the Proof of Lemma A2, net earnings of such workers at sl = 0 equal

(53)αAF(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]δnē1αδn1ē,

where πn is a solution to (28) in the Proof of Proposition 1. From (2) and (22) in the Proof of Proposition 1, net earnings of such workers at sl=sl equal

(54)αA(1α)h̲l+δlslēαδn1slē1αδn1sl1ē=αA(1α)2α2δlδn1αδnα1+h̲lδlē1ē.

From these equations, the net earnings are maximized at sl=sl if

(55)(1α)2α21αα1+h̲lδlēδl1α>F(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]ē1α,

which holds when A, δn, and δl are large. This is because πn increases with A and δn from (28), 1+h̲lδlēδl1α increases with δl from (1α)1δl1+h̲lδlē11δl2h̲lē=(1α)αh̲lδlēδl1+h̲lδlē=slδl1+h̲lδlē>0, and the condition does hold when πn = 1, i.e. (1α)2α21αα1+h̲lδlē>F(ē)h̲l[1F(ē)]δlē1α. Since F(ē)1α at sl = 0 from (27) in the Proof of Proposition 1, the last statement is proved if (1α)2α21αα1+h̲lδlē>(1α)h̲lαδlē1α(1α)1ααα1+h̲lδlē1h̲lδlēα>1 holds, which is true, because sl(1α)αh̲lδlē>0h̲lδlē<1αα and the LHS decreases with h̲lδlē:

(56)αh̲lδlēh̲lδlē21+h̲lδlē1=α(1α)h̲lδlē1h̲lδlē1+h̲lδlē1<0 from h̲lδlē<1αα.

(b) Consider case ē1+α1αh̲lδl first. Since sl(e) increases with e, sl(α(h̲lδl+ē))=0, and sl(ē)=sl from (52) in the Proof of Proposition 3, there exists an e(α(h̲lδl+ē),ē), such that sl(e)=sl̲. Then, the relationship between sl and net earnings of workers with a local job and e > e is similar to that of workers with a national job: their net earnings decrease with sl for sl<sl̲, increase with sl for sl(sl̲,sl(e)), and decrease with sl for sl>sl(e) from Propositions 2 and 3 and Lemma A2. As for workers with ee, net earnings decrease with sl. Now consider case ē>1+α1αh̲lδl. If A, δl, and δn are small enough that sl(α(h̲lδl+ē))=1α(1+α)h̲lδlē<sl̲, the result is same as the case of ē1+α1αh̲lδl. Let Λ(ē)αh̲lδl+ē1+δl4h̲ē(1α)ē(1+α)h̲lδl2. If sl(α(h̲lδl+ē))>sl̲>slΛ(ē)=(1α)(1+α)h̲lδlē2, there exists an eΛ(ē),αh̲lδl+ē such that sl(e)=sl̲. The results for those with e>αh̲lδl+ē and those with eΛ(ē) are same as the corresponding cases (e > e and ee respectively) of ē1+α1αh̲lδl. As for those with eΛ(ē),αh̲lδl+ē, sl°(e)(1α)(1+α)h̲lδlē2=slΛ(ē)<sl(e)=sl̲ holds for any e from (51) and (52) in the Proof of Proposition 3. Hence, the result of those with e > e is similar to that of those with e>αh̲lδl+ē, and the result of those with ee is same as that of those with eΛ(ē). In sum, the result is similar to when ē1+α1αh̲lδl except that the critical wealth level is e, not e. Finally, if slΛ(ē)>sl̲, since sl°(e) decreases with e, sl°(α(h̲lδl+ē))=0, and sl°Λ(ē)=slΛ(ē)=(1α)(1+α)h̲lδlē2 from (51) and (52), there exists an eΛ(ē),αh̲lδl+ē such that sl(e)=sl̲. Hence, as for workers with eΛ(ē),αh̲lδl+ē, net earnings of those with e < e decrease with sl for sl < sl°(e), increase with sl for sl<(sl(e),sl(e)), and decrease with sl for sl>sl(e), while net earnings of those with ee decrease with sl for sl<sl̲, increase with sl for sl(sl̲,sl(e)), and decrease with sl for greater sl. The results for those with e>αh̲lδl+ē and those with eΛ(ē) are same as the previous case. In sum, net earnings of workers with wealth greater than a certain level decrease with sl for sl<max{sl̲,sl°(e)}, increase with sl for sl(maxsl̲,sl(e),sl(e)), and decrease with sl for sl>sl(e), while net earnings of workers with a = e smaller than the threshold decrease with sl. Thus, net earnings of workers with wealth greater than a threshold are maximized at either sl = 0 or sl=sl(e). From (28) in the Proof of Proposition 1, net earnings of such workers at sl = 0 is same as net earnings of workers with a national job, which equals (53). From (23) in the Proof of Proposition 1, net earnings of such workers with e at sl=sl(e) equal

(57)(1α)Aαδn(1sl(e))ē(1α)h̲l+δlsl(e)ēαh̲l+δlsl(e)ēe.

Thus, the net earnings are maximized at sl=sl(e) if

(58)Aδnēα(1α)α(1sl(e))1ααh̲l+δlsl(e)ē1ααF(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]1α+ēe>0,

which holds when A, δn, and δl are large, because πn increases with A and δn, the derivative of the first term of the expression inside the large curcly bracket with resepct to sl is 0 at sl=sl(e) and negative for sl>sl(e), and thus the expression is positive when A and δl are large from (55):

(59)(1α)α(1sl(e))1ααh̲l+δlsl(e)ē1ααF(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]1α>(1α)α1sl1ααh̲l+δlslē1ααF(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]1α(from Proposition 3 (ii)(a))=αδlē1α(1α)2α21αα1+h̲lδlēF(ē)+(1πn)1F(ē)h̲lπn[1F(ē)]δlē1α>0.

(c) From the proof of (b), the threshold wealth when ē1+α1αh̲lδl is e(α(h̲lδl+ē),ē) such that sl(e)=sl̲. The threshold when ē>1+α1αh̲lδl is e(α(h̲lδl+ē),ē) if sl(α(h̲lδl+ē))<sl̲, eΛ(ē),αh̲lδl+ē such that sl(e)=sl̲ if sl(α(h̲lδl+ē))>sl̲>slΛ(ē), and Λ(ē) if slΛ(ē)>sl̲. When ē>1+α1αh̲lδl, case sl(α(h̲lδl+ē))<sl̲ is realized when A, δl, and δn are small, and case slΛ(ē)>sl̲ is realized when they are large, because sl̲ decreases with A, δl, and δn from Proposition 1, and sl(α(h̲lδl+ē))=(1α)(1+α)h̲lδlē and slΛ(ē)=12(1α)(1+α)h̲lδlē increase with δl. Further, e and e decrease with A, δl, and δn, because sl(e) increases with δl at e = e, e from Lemma A3 below and increases with e, and sl̲ decreases with A, δl, and δn. Hence, the threshold of wealth decreases with A and δn (except when the threshold is αh̲lδl+ē and Λ(ē)) and δl. □

Lemma A3

sl(e)δl>0 and sl(e)δl>0.

Proof of Lemma A3

From (52) in the Proof of Proposition 2, the derivative of sl(e) with respect to δ l equals a constant times

(60)(1+α)h̲l12(1+α)h̲l2(1α)ē(1+α)h̲lδl+4ēαh̲lδl+ēe1+1h̲l4ēαh̲lδle1h̲l×(1α)ē(1+α)h̲lδl2+4ēδlαh̲lδl+ēe1+1h̲l1/2.

Thus,

(61)sl(e)δl0(1+α)h̲l2(1α)ē(1+α)h̲lδl+4ēαh̲lδl+ēe1+1h̲l4ēαh̲lδle1h̲l2(1+α)h̲l×(1α)ē(1+α)h̲lδl2+4ēδlαh̲lδl+ēe1+1h̲l1/2.

The lemma is proved if it is shown that sl(e)δl0 cannot hold at e = e, e. From the above equation, sl(e)δl0 is possible only when the LHS of the equation is positive, which is true only when (1α)ē(1+α)h̲lδl<0ē<1+α1αh̲lδl or αh̲lδl+ēe1+1αh̲lδle1>0e>α2h̲lδl+ē. When the LHS is positive, the above equation can be expressed as

(62)sl(e)δl0(1+α)h̲l2(1α)ē(1+α)h̲lδl+4ēαh̲lδl+ēe1+1h̲l4ēαh̲lδle1h̲l22(1+α)h̲l2×(1α)ē(1+α)h̲lδl2+4ēδlαh̲lδl+ēe1+1h̲l
(63)(1+α)(1α)ē(1+α)h̲lδlα2h̲lδl+ēe1+1+α2h̲lδl+ēe1+12ē(1+α)21δlαh̲lδl+ēe1+1h̲lα2h̲lδl+ēe1+12h̲lδl+ēe1+αē(1+α)21δlh̲lδle1h̲l0.

The expression is clearly negative when eα2h̲lδl+ē. Hence, sl(e)δl0 is possible only when ē<1+α1αh̲lδl and e<α2h̲lδl+ē. In this case, the LHS of (61) is weakly smaller than (1+α)h̲l2(1+α)h̲lδl(1α)ē, while, since e>αh̲lδl+ē (e does not exist) when ē<1+α1αh̲lδl, the RHS of (61) is greater than (1+α)h̲l2(1+α)h̲lδl(1α)ē. Hence, sl(e)δl>0 holds in this case. The fact that e does not exist when ē<1+α1αh̲lδl proves that sl(e)δl0 cannot happen. □

Proof of Corollary 1

Since F(ē)=0<1α, the Proof of Proposition 4 can be applied with a>ē for anyone. The result is straightforward from the proof, since e=ē=e+ and thus sl(e)=sl(ē)=sl for those choosing a local job, and ē>αh̲lδl+ē by assumption (see footnote 20). □

Proof of Proposition 6

In order to prove the proposition, the following lemma is used.

Lemma A4

When e+<ē, net earnings of workers with given wealth and a national job increase discontinuously and those of workers with a local job decrease discontinuously, when the return to educational investment for local jobs turns from negative to positive with a change in sl.

Proof of Lemma A4

When e+<ē and the return is negative, wnhne+,sle+=wlh̲lαAHlHn1αδn(1sl)1e+=(1α)AHnHlαh̲l, where Hl=F(e+)h̲l and Hn=e+ēhn(e,sl)f(e)de+1F(ē)hn(ē,sl), holds from (11) and (12). When e+<ē and the return is positive, wnhn(e+,sl)e+=wlhl(e+,sl)e+αAHlHn1αδn(1sl)1e+=(1α)AHnHlαh̲l+δlsle+e+, where Hl=0e+hl(e,sl)f(e)de and Hn=e+ēhn(e,sl)f(e)de+1F(ē)hn(ē,sl), holds from (2) and (5). When the return is zero, i.e. wlδlsl − 1 = 0, this equation becomes αAHlHn1αδn(1sl)1e+=(1α)AHnHlαh̲l, the same equation as the case of the negative return. Because HnHl under the negative return is greater than under the positive return for given e+ and HnHl decreases with e+, e+ and HnHl satisfying the above equation are greater when the return is negative. Hence, net earnings of those with a local job are greater and of those with given a(>e+) and a national job are smaller when the return is negative and sl approaches a value at which the return is zero than when the return is zero. That is, net earnings of those with a national (local) job increase (decrease) discontinuously when the return turns from negative to positive with a change in sl. □

(i) Let the lower (higher) sl such that the return to education for local jobs is 0 when e+<ē be sl̲(f) (sl̄(f)), whose existence is shown in the Proof of Proposition 1. As for those who have abundant wealth and choose a national job for any sl, i.e. amin{e+(1),ē}, net earnings decrease with sl except at sl=sl̲(f), where they increase discontinuously from Lemma A4, if e+(0)α1αh̲lδl or sl̲(f)sl satisfying sl=(1α)αh̲lδle+(sl) from Propositions A1 (i) and 2. The former condition holds when δl is small, because e+(0) does not depend on A, δn, and δl from (D3) in the Proof of Proposition A1 in Appendix D. The latter condition holds when A, δn, and δl are small, since sl̲(f) decreases with A, δn, and δl from Proposition 1 and is greater than 1 − α when these variables are small from the part of the Proof of Proposition 1 (i)(a) just after Lemma A1, while sl<1α. As for those who choose a local job for any sl, i.e. a = e < e+(0), net earnings decrease with sl except at sl=sl̄(f), where net earnings increase discontinuously from Lemma A4, when E(e|e<e+(0))1+α1αh̲lδl and eαh̲lδl+E(e|e<e+(0)), when E(e|e<e+(0))>1+α1αh̲lδl and e ≤ Ω(e+(0)), and when sl̲(f)sl,h(e) for greater e, where sl,h(e) is the greater solution of M(sl) = 0 (M(sl) equals L(sl) with e+(sl) replaced with E(e|e<e+(sl))0e+(sl)ef(e)deF(e+(sl))), from Propositions A1 (ii) and 2. Thus, irrespective of a = e, net earnings decrease with sl except at sl=sl̄(f), if sl̲(f)sl,h(e). The condition holds when A, δn, and δl are small, because as shown above, sl̲(f)>1α when they are small, while 1αsl,h(e) holds when δl is small. The latter statement is true because M(1α)=αh̲lδl+E(e|e<e+(1α))αeh̲lδl<αh̲lδlαeh̲lδl0 when δl is sufficiently small. Finally, as for those who choose a national (local) job at small (large) sl, if the above conditions hold, net earnings decrease with sl except at sl=sl̲(f), sl=sl̄(f), or both depending on at which s l the switch to a local job occurs, where net earnings increase discontinuously from Lemma A4. Under the above condition, net earnings of workers with a < e+(0) are maximized at sl = 0, because their earnings when the return is negative decrease with sl from Proposition 2 and thus the earnings when slsl̄(f) from above are lower than the earnings at sl = 0. Net earnings of workers with amin{e+(1),ē} are maximized at either sl = 0 or sl=sl̲(f), since the earnings increase discontinuously at sl=sl̲(f). From the Proof of Lemma A4, net earnings of such workers with educational spending e at sl = 0 equal

(64)αAHle+,slHne+,sl1αδn1e=αA1ααh̲lδne+(0)1αδn1e,

where the equality sign is from (7). From (14) in the proof of Proposition 1 and (2), their net earnings at sl=sl̲(f) equal

(65)αA(1α)h̲l+δlsle+αδn(1sl)e+1αδn(1sl)1e=αA(1α)Aδlsl1ααδn(1sl)1e
(66)<αA(1α)2Aδl1ααδnα1e(from sl̲(f)<1α),

where the equality sign is from the fact that the return for local jobs is 0 at sl=sl̲(f). From (64) and (66), the net earnings are maximized at sl = 0 if

(67)1ααh̲lδne+(0)1α>(1α)2Aδl1ααα,

which holds when A, δn, and δl are small, since e+(0) does not depend on A, δn, and δl. As for those who choose a national job at small sl and a local job at large sl, the proof for those who choose a local (national) job for any sl applies if the switch to a local job occurs at slsl̲(f) (slsl̄(f)). If the switch occurs at sl(sl̲(f),sl̄(f)), the proof of those who choose a national job for any sl applies, since earnings when the return is negative decrease with sl from Proposition 2. (ii) From the above results, if a<mine+(0),αh̲lδl+E(e|e<e+(0)) when E(e|e<e+(0))1+α1αh̲lδl or if a<mine+(0),Ω(e+(0)) when E(e|e<e+(0))>1+α1αh̲lδl, workers choose a local job for any sl, and their net earnings decrease with sl except at sl=sl̄(f), where the earnings increase discontinuously. Net earnings of such workers are maximized at sl = 0, because the earnings when the return is negative decrease with sl from Proposition 2. (iii) As for workers who choose a national job for any sl, i.e. amin{e+(1),ē}, their net earnings decrease with sl for sl<sl̲(f) and sl>sl̄(f) from Proposition 2, increase (decrease) discontinuously at sl=sl̲(f) (at sl=sl̄(f)) from Lemma A4, and increase (decrease) with sl for sl(sl̲(f),sl] (for sl[sl,sl̄(f))), if e+(0)>α1αh̲lδl, E(e|e<e+(0))>αmax11αh̲lδl,e+(0)1+α, and sl>sl̲(f), where sl0,sl satisfies sl=(1α)αh̲lδlE(e|e<e+sl), from Proposition A1 (i). (sl,sl<1α<sl̄(f) from Proposition A1 (i) and Lemma A1 in the Proof of Proposition 1.) The condition holds when A, δn, and δl are large, because e+(0) does not depend on these parameters, sl increases with δl (since e+(sl) increases with δl from the Proof of Proposition 1 (i)(b)), and sl̲(f) decreases with A, δn, and δl and approaches 0 as these parameters increase from Proposition 1 and its proof. The net earnings are maximized at sl = 0 or sl satisfying d(wnhn)dsl=0, where the latter satisfies sl(sl,1α) and thus sl<1α<sl̄(f) from Proposition A1 (i) and Lemma A1. From (64) and (65) above, net earnings of such workers with educational spending e at sl = 0 is smaller than their net earnings at sl=sl (and thus the earnings at sl satisfying d(wnhn)dsl=0) iff h̲le+(0)1α<h̲l+δlsle+(sl)e+(sl)1α(1sl)α, which holds if

(68)h̲le+(0)1α<h̲l+δlslēē1α1slα.

The condition holds when δl is sufficiently large, because e+(0) does not depend on A, δn, and δl, sl increases with δl, and the RHS increases with sl:

(69)1αh̲l+δlslēδlēα1sl=δlē1αslαh̲lh̲l+δlslē1sl=αh̲lēE(e|e<e+sl)1h̲l+δlslē1sl>0.

As for workers who choose a local job for any sl, i.e. a < e+(0), their net earnings decrease with sl for sl<sl̲(f) and sl>sl̄(f) from Proposition 2, decrease (increase) discontinuously at sl=sl̲(f) (at sl=sl̄(f)) from Lemma A4, and increase (decrease) with sl for sl(sl̲(f),min(sl,h(e),sl̄(f))] (for sl[sl,h(e),sl̄(f)) when sl,h(e)<sl̄(f)), if sl,h(e)>sl̲(f) and e=a>maxαh̲lδl+e+(0),Λ(ē) from Proposition A1 (ii). The condition holds when A and δn are large, because e+(0), Λ(ē), and sl,h(e) do not depend on these parameters, and sl̲(f) decreases with A and δn. The condition holds when δl is large, because Λ(ē) decreases with δl, sl,h(e)(0,1) from the Proof of Proposition A1 (ii) in Appendix D, while sl̲(f) approaches 0 as δl increases, which is from sl̲(f) being decreasing in δl, and from (14) and Lemma A1 in the Proof of Proposition 1. Their net earnings are maximized at either sl = 0, or sl(sl,h(e),sl̄(f)) such that d(wlhl)dsl=0. (The earnings at sl=sl̄(f) are smaller than the earnings when slsl̄(f) from above and thus cannot be the maximum.) From (2) and (6), net earnings of such workers at sl = 0 equal

(70)(1α)AHn(e+,0)Hl(e+,0)αh̲l=(1α)Aδnα1αe+(0)h̲lαh̲l.

From (2) and (6), net earnings of such workers with e = a at s l satisfying d(wlhl)dsl=0 equal (1α)Aαδn(1sl)e+(sl)(1α)h̲l+δlsle+(sl)αh̲l+δlslee. The net earnings at such sl is greater than at sl = 0 iff

(71)(1α)Aδnα1αα(1sl)e+(sl)h̲l+δlsle+(sl)αh̲l+δlslee+(0)h̲lαh̲le>0,

which is true if

(72)(1α)Aδnα1αα(1sl)eαh̲l+δlsle1αe+(0)α(h̲l)1αe>0.

When δ l is sufficiently large, 1α(sl̲(f),sl̄(f)) from Lemma A1 in the Proof of Proposition 1. Hence, the above condition holds if

(73)(1α)Aδnα1αα(αe)α[h̲l+δl(1α)e]1αe+(0)α(h̲l)1αe>0,

which is true when δl is sufficiently large, because the expression inside the curly bracket is large positive (e+(0) does not depend on δl). Finally, as for workers who choose a national (local) job when sl is small (large), i.e. a[e+(0),min{e+(1),ē}), the result is clearly similar to workers who choose a national (local) job for any sl, when the shift to a local job occurs at sl>sl̄(f) (sl<sl̲(f)). When the shift occurs at sl[sl̲(f),sl̄(f)], their net earnings increase discontinuously at sl=sl̲(f) and sl=sl̄(f), and they are maximized at sl = 0 or sl(sl̲(f),sl̄(f)) satisfying either d(wnhn)dsl=0, d(wlhl)dsl=0, or a = e = e+(sl) (sl at which the switch to a local job occurs). (The earnings at sl=sl̄(f) are smaller than the ones when slsl̄(f) from above and thus cannot be the maximum.) From the argument above, the net earnings are maximized at the latter sl when δl is sufficiently large. □

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Received: 2022-03-30
Revised: 2022-08-24
Accepted: 2022-09-12
Published Online: 2022-10-12

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