Abstract
We provide methods for the empirical analysis of a class of two-player repeated games with i.i.d. shocks, allowing for non-Markovian strategies. The number of possible equilibria in these games is large and, usually, theory is silent about which equilibrium will be chosen in practice. Thus, our method remains agnostic about selection among these multiple equilibria, which leads to partial identification of the parameters of the game. We propose a profiled likelihood criterion for building confidence sets for the structural parameters of the game and derive an easily computable upper bound on the critical value. We demonstrate good finite-sample performance of our procedure using a simulation study. We illustrate the usefulness of our method by studying the effect of repealing the Wright Amendment on entry and exit into Dallas airline markets and find that the static game approach overestimates the negative effect of the law on entry into these markets.
Funding source: University of Leicester
Award Identifier / Grant number: Unassigned
Acknowledgments
We would like to thank the Associate Editor and two anonymous referees for their suggestions that greatly improved the paper. Also, many thanks to Mike Abito, Wojciech Olszewski, Subir Bose and Andre Stenzel for useful discussions and suggestions and to Arpita Ghosh and Shuai Zhao for providing competent research assistance. We are grateful to participants in the LSE Joint Econometrics and Statistics Workshop, the (Ce)2 Workshop, the UEA Economics seminar and various conferences for useful comments. This research used the ALICE High Performance Computing Facility at the University of Leicester.
Appendix A: Mathematical Proofs
A.1 Proof of Theorem 1
First note that under quasi-concavity:
Further, Assumptions INF2(c)–(g) allow us to apply Proposition 5.1 and Lemma F.1 in Chen, Christensen, and Tamer (2018) in order to obtain quadratic expansion of the likelihood in γ:
where
This implies:
Now use Assumption INF3 and proceed similarly to Shapiro (1985). Note that the cone
for
and together with (6) concludes the proof.
A.2 Proof of Theorem 2
First we will demonstrate that
Next recall that
but as the elliptic radi grow with k
T
we have that
Assumption INF5 implies that
as T → ∞.
Next note that K
LF(θ
1) ⊆ K
2(θ
1). This is trivially satisfied when
which implies that
Finally, we have:
which together with (8) concludes the proof.
A.3 Proof of Theorem 3
For a closed convex cone K let K
o denote its polar cone (see e.g. Section 14 in Rockafellar 1970). From the proof of Theorem 1 and Moreau’s decomposition theorem (note that
which implies LR T (θ 1) ≤ ‖V T ‖2 + o p (1) and
and the result follows from V T being asymptotically N(0, I).
Appendix B: Alternative Definitions of Market Presence
In Table 4 an airline is present in the market if it operates at least one flight from the market origin to market destination. Here we consider other definitions of market presence. First, we use DB1B ticketing data, which contains 10% sample of airline tickets from reporting carriers, and redefine market presence as selling at least 5 tickets for the specified route (see Table 8). Next, we use T100 Segment data and redefine market as a segment of the trip, for example a flight from ORD to MIA through DCA contains two segments ORD-DCA and DCA-MIA (using previous definition this would only be a single market ORD-MIA).
Share of markets by presence of major (ticketing) carriers over time (in %).
| Presence in Q2 1993 – Q2 2002 – Q2 2012 | American | Delta | United | US Airways | Southwest |
|---|---|---|---|---|---|
| In – in – in | 43.4 | 61.1 | 74.8 | 42.8 | 86.8 |
| In – out – in | 9 | 5.9 | 9.2 | 12.3 | 4.8 |
| In – out – out | 37 | 23.1 | 12.8 | 27 | 6 |
| In – in – out | 10.6 | 9.9 | 3.2 | 17.9 | 2.4 |
-
DB1B Market data, flights with less than 5 tickets in 1993 dropped. Markets are defined as directional routes between origin and destination airports (irrespective of the number of stops on the way). “In” means that a carrier served at least one flight on the route.
The numbers in Table 8 significantly differ from those in Table 4 as ubiquitous codeshare and interlining agreements drive a wedge between the definitions of operating and ticketing carrier. The differences are smaller between Table 9 and Table 4. Despite these differences the main message remains the same – there is substantial amount of entry and exit across time in the US airline market.
Share of markets by presence of major carriers over time (in %).
| Presence in Q2 1990 – Q2 2000 – Q2 2010 | American | Delta | United | US Airways | Southwest |
|---|---|---|---|---|---|
| In – in – in | 34 | 35.8 | 38.6 | 16.5 | 74.6 |
| In – out – in | 5 | 6.8 | 2.7 | 3.5 | 3.1 |
| In – out – out | 46.4 | 33.4 | 35.8 | 53.8 | 14 |
| In – in – out | 14.6 | 24.1 | 23 | 26.3 | 8.3 |
-
T100 Segment data, flights with less than 20 passengers in 1990 dropped. Markets are defined as segments of directional routes between origin and destination airports. “In” means that a carrier served at least one flight on the route.
Appendix C: Moment Inequality Characterisation
For a non-empty
where j = 1, 2, …, J. Now for inference one can implement either the profiled procedure in Kaido, Molinari, and Stoye (2019) (KMS) or Bugni, Canay, and Shi (2017) (BCS). We discuss how the computational burden of these procedures compares to our approach as computation is the main obstacle for a practical inference in our model.[25] For this discussion we employ similar notation as in Section 5 in the paper, namely θ 1 ≡ α, θ 2 ≡ V, θ = (θ 1, θ 2).
C.1 KMS Inference
Let
where ρB d imposes a technical “box” constraint on the local parameter space and ψ j is a Generalised Moment Selection function of Andrews and Soares (2010), and can be calculated as:
where P* denotes the law induced by bootstrap sampling and λ
1 is the first element of λ. Finally, the marginal confidence set is built by finding lowest and highest value of θ
1 for which the sample moment inequalities are satisfied with slackness
Let us now compare our inference method to KMS. Note that the computationally difficult step in our model is the re-evaluation of the continuation value set Θ2(θ
1) for different values of θ
1, which will be embedded in evaluating
Similarly, the first step in the KMS procedure in which candidate values of θ are drawn can be adjusted to include only θ’s on the grid of values for θ 1 to limit number of evaluations of Θ2(θ 1). However, as currently implemented, the KMS procedure proceeds with a smooth iterative algorithm to generate further “good” candidate values of θ (“A-M steps”) and, thus, requires recalculation of Θ2(θ 1) for these newly generated values. As the number of iterations required for this algorithm to converge may differ from application to application, it may be difficult to control the number of evaluations of Θ2(θ 1) in practice without significant changes to this algorithm. Therefore, it seems that using the moment inequality characterisation in (9) and KMS is unlikely to dominate our method in terms of computational convenience.
C.2 BCS Inference
The main BCS critical value is obtained by taking a minimum over two profiled bootstrap statistics,
Using the notation from the previous section BCS resampling statistics can be written as:
where
Appendix D: Additional Monte Carlo Simulations
We perform limited number of simulations for δ = 0.95 due to slow convergence of optimization algorithms for this case, which leads to extensive computing times. The results are given in Table 10.
MC simulations: coverage probabilities, δ = 0.95.
| Normal shocks | ||||||
|---|---|---|---|---|---|---|
| Simulated crit. val. |
|
|||||
| 90% | 95% | 99% | 90% | 95% | 99% | |
| Θ01 = [0.49, 5.06] | 0.979 | 0.981 | 0.981 | 0.981 | 0.981 | 0.985 |
| α = 0.1 | 0 | 0 | 0 | 0 | 0 | 0 |
| α = 5.6 | 0.268 | 0.270 | 0.273 | 0.270 | 0.270 | 0.276 |
| Θ01 = [0.49, 5.06] | 0.92 | 0.971 | 0.98 | 0.971 | 0.973 | 0.996 |
| α = 0.1 | 0 | 0 | 0 | 0 | 0 | 0 |
| α = 5.6 | 0.131 | 0.132 | 0.135 | 0.133 | 0.135 | 0.135 |
| Θ01 = [0.49, 5.06] | 0.935 | 0.961 | 0.982 | 0.982 | 0.982 | 0.994 |
| α = 0.1 | 0 | 0 | 0 | 0 | 0 | 0 |
| α = 5.6 | 0.084 | 0.085 | 0.088 | 0.085 | 0.087 | 0.088 |
| Θ01 = [0.49, 5.06] | 0.942 | 0.97 | 0.989 | 0.971 | 0.985 | 0.994 |
| α = 0.1 | 0 | 0 | 0 | 0 | 0 | 0 |
| α = 5.6 | 0.076 | 0.077 | 0.079 | 0.077 | 0.077 | 0.079 |
-
500 Monte Carlo replications.
Appendix E: Inference Without Assumption INF3
In this section we discuss how we can adjust our simulated critical value if θ*(θ
1) is not unique and
Firstly, the main complication here comes from the fact that now the local parameter space for γ at γ
0 cannot be approximated simply by taking
where
Now in order to approximate the statistic on the right-hand side above, we can replace
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© 2022 Walter de Gruyter GmbH, Berlin/Boston
Articles in the same Issue
- Frontmatter
- Research Articles
- Empirical Framework for Two-Player Repeated Games with Random States
- The Robustness of Conditional Logit for Binary Response Panel Data Models with Serial Correlation
- Density Forecast of Financial Returns Using Decomposition and Maximum Entropy
- On the Implementation of Approximate Randomization Tests in Linear Models with a Small Number of Clusters
- Quantile Difference in Differences with Time-Varying Qualification in Panel Data
- A Random Forest-based Approach to Combining and Ranking Seasonality Tests
- Teaching Corner
- On the Use of the Helmert Transformation, and its Applications in Panel Data Econometrics
- Practitioner's Corner
- Linear Rescaling to Accurately Interpret Logarithms
Articles in the same Issue
- Frontmatter
- Research Articles
- Empirical Framework for Two-Player Repeated Games with Random States
- The Robustness of Conditional Logit for Binary Response Panel Data Models with Serial Correlation
- Density Forecast of Financial Returns Using Decomposition and Maximum Entropy
- On the Implementation of Approximate Randomization Tests in Linear Models with a Small Number of Clusters
- Quantile Difference in Differences with Time-Varying Qualification in Panel Data
- A Random Forest-based Approach to Combining and Ranking Seasonality Tests
- Teaching Corner
- On the Use of the Helmert Transformation, and its Applications in Panel Data Econometrics
- Practitioner's Corner
- Linear Rescaling to Accurately Interpret Logarithms