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FIVB ranking: misstep in the right direction

  • Salma Tenni , Daniel Gomes de Pinho Zanco and Leszek Szczecinski EMAIL logo
Published/Copyright: April 30, 2025

Abstract

This work presents and evaluates the ranking algorithm that has been used by Fédération Internationale de Volleyball (FIVB) since 2020. The prominent feature of the FIVB ranking is the use of the probabilistic model, which explicitly calculates the probabilities of the future matches results using the estimated teams’ strengths. Such explicit modeling is new in the context of official sport rankings, especially for multi-level outcomes, and we study the optimality of its parameters using both analytical and numerical methods. We conclude that from the modeling perspective, the current thresholds fit well the data but adding the home-field advantage (HFA) would be beneficial. Regarding the algorithm itself, we explain the rationale behind the approximations currently used and show a simple method to find new parameters (numerical score) which improve the performance. We also show that the weighting of the match results is counterproductive.


Corresponding author: Leszek Szczecinski, Institut National de la Recherche Scientifique, Montreal, Canada, E-mail: 

Appendix A: Notation in FIVB ranking

We show in Table 6, the relationship between our notation and the one used in the FIVB ranking description (FIVB 2024), where the following abbreviations are used

  1. WR: World ranking (here, a FIVB ranking)

  2. WRS: World ranking score (here, we call it skills θ m,t)

  3. SSV: Set score variant (we call it numerical score r y )

  4. EMR: Expected match result (here, the expected score r ̌ ( z ) , see (22))

  5. MWF: Match weighting factor (here, it corresponds to 10 ξ v t )

  6. Scaled difference between WRSs Δ = 8(WRS1 − WRS2)/1,000

Table 6:

Equivalence of this work’s notation and the one used in the description of the FIVB ranking.

Our notation FIVB notation
θm,t, θn,t WRS1, WRS2
c 0 F I V B , , c 4 F I V B C1, …, C5
z t /s = (θm,tθn,t)/s Δ = 8(WRS1 − WRS2)/1,000
s 1,000/8 = 125
P 0 ( z t ) , , P 5 ( z t ) P1, …, P5
Φ(z) N(0, 1)(z)
r y t F I V B SSV
r ̌ ( z t / s ) EMR
10 ξ v t MWF
g F I V B ( z t / s ) = r y t F I V B r ̌ ( z t / s ) WR value
θ m , t + 1 θ m , t = 10 ξ v t g F I V B ( z t / s ) WR points = WR values * MWF/8

With this notation, the update formula is given by

(59) WRS 1 WRS 1 + WR points

and corresponds to (20) which, focusing on the update of the skills of the home team m, may be written as

(60) θ m , t + 1 = θ m , t μ s ξ v t g y t F I V B ( z t / s ) .

Appendix B: Optimization of the cross-validation metric

The simplest optimization of the cross-validation metric U( p ) may be done via the steepest descent

(61) p ̂ p ̂ κ p U ( p ) ,

where, κ is the step-size, and to calculate the gradient ∇ p U( p ), we have to calculate derivatives of U( p ) with respect to a parameter q p . This can be done as follows:

(62) q U ( p ) = 1 T t = 1 T q y t v a l ( z ̂ t , \ t , p )
(63) q y t v a l ( z ̂ t , \ t ) = z ̂ t , \ t q ̇ v a l ( z ̂ t , \ t , p ) + q y t v a l ( z ̂ t , \ t , p )
(64) z ̂ t , \ t q = z ̂ t q + q ξ v t ̇ y t ( z ̂ t , p ) a t 1 ξ v t ̈ y t ( z ̂ t , p ) a t .

In (64), we will need

(65) z ̂ t q = x t T θ ̂ q
(66) a t q = x t T H ̂ 1 q x t = x t T H ̂ 1 H ̂ q H ̂ 1 x t
(67) H ̂ q = t = 1 T x t q ξ v t ̈ y t ( z ̂ t , p ) x t T + I q = γ I
(68) q ̇ y t ( z ̂ t , p ) = z ̂ t q ̈ y t ( z ̂ t , p ) + q ̇ y t ( z ̂ t , p )
(69) q ̈ y t ( z ̂ t , p ) = z ̂ t q y t ( z ̂ t , p ) + q ̈ y t ( z ̂ t , p )

where, in (66) we used (Petersen and Pedersen 2012, Eq. (40)), and y ( z , p ) = 3 z 3 y ( z , p ) .

From implicit function theorem, see Lorraine et al. (2019, Th. 1), using θ ̂ θ ̂ ( p )

(70) 0 = q θ J ( θ ̂ ( p ) , p )
(71) 0 = θ 2 J ( θ ̂ ( p ) , p ) θ ̂ ( p ) q + q θ J ( θ ̂ , p )
(72) θ ̂ q = H ̂ 1 q θ J ( θ ̂ , p )
(73) q θ J ( θ ̂ , p ) = t = 1 T q ξ v t ̇ y t ( x t T θ ̂ , p ) x t + I γ = q θ ̂ .

By plugging z ̂ t , \ t ( p ) into (33) we obtain the function U( p ) which depends on p and we can calculate the gradient ∇ p U( p ).

Similarly, we can use the Newton method

(74) p ̂ p ̂ p 2 U ( p ) 1 p U ( p )

where, to calculate the Hessian, p 2 U ( p ) we need second order derivatives.

However, the expressions for the gradient and, especially, the Hessian, quickly become cumbersome; see Burn (2020). Thus, instead of explicit differentiation, we use the automatic differentiation available in JAX and JAXopt python-compliant packages (Blondel et al. 2021; Bradbury et al. 2018) with a particularly interesting feature which automatically finds the implicit differentiation required to find the derivative of θ ̂ with respect to hyperparameters in p as specified by (72).

We do not show more details to not overcomplicate the presentation, especially that they are not really required because the numerical optimization is used to confirm the observation we made using the analytical insight. In fact, the performance of the online algorithm shown in Section 4 uses the parameters (shown in Table 4) which are explicitly defined prior to the application of the algorithms.

  1. Research ethics: Not applicable.

  2. Informed consent: Not applicable.

  3. Author contributions: All authors contributed to the analysis, data acquisition and treatment, writing and correction.

  4. Use of Large Language Models, AI and Machine Learning Tools: None declared.

  5. Conflict of interest: The authors state no conflict of interest.

  6. Research funding: Natural Sciences and Engineering Research Council of Canada.

  7. Data availability: Available at the repository https://github.com/brbalab/FIVB.

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Received: 2024-08-19
Accepted: 2025-01-15
Published Online: 2025-04-30
Published in Print: 2025-09-25

© 2025 Walter de Gruyter GmbH, Berlin/Boston

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