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On relations between stochastic dominance efficiency tests and DEA-risk models Martin Branda, Milo s Kopa Charles University in Prague Faculty of Mathematics and Physics Department of Probability and Mathematical Statistics 13th


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On relations between stochastic dominance efficiency tests and DEA-risk models

Martin Branda, Miloˇ s Kopa

Charles University in Prague Faculty of Mathematics and Physics Department of Probability and Mathematical Statistics

13th International Conference on Stochastic Programming 8-12 July 2013, Bergamo

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Contents

1 Motivation 2 Second Order Stochastic Dominance 3 Data Envelopment Analysis 4 Numerical comparison

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Motivation

Contents

1 Motivation 2 Second Order Stochastic Dominance 3 Data Envelopment Analysis 4 Numerical comparison

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Motivation

A bridge

Data envelopment analysis (production theory, returns to scale, radial/slack-based/directional distance models, primal/dual formulations, multiobjective opt. – Pareto efficiency, chance constraints), large literature: handbook on DEA, Omega, EJOR, JORS, ... Stochastic dominance efficiency (pairwise, convex, portfolio): Is there R such that R ≻SSD R0? No – R0 is efficient. Compare with the problem max f (R) : s.t. R SSD R0.

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Second Order Stochastic Dominance

Contents

1 Motivation 2 Second Order Stochastic Dominance 3 Data Envelopment Analysis 4 Numerical comparison

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Second Order Stochastic Dominance

Second order stochastic dominance

F1, F2... cumulative probability distributions functions of random variables X1, X2. Second order (strict) stochastic dominance (SSD): X1 ≻SSD X2 iff EF1u(x) − EF2u(x) ≥ 0 for every concave utility function u with at least one strict inequality. Consider twice cumulated probability distributions functions: F (2)

i

(t) = t

−∞

Fi(x)dx i = 1, 2. Theorem (Hanoch & Levy (1969)): X1 ≻SSD X2 ⇔ F (2)

1 (t) ≤ F (2) 2 (t)

∀t ∈ R with at least one strict inequality.

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Second Order Stochastic Dominance

SSD portfolio efficiency

We consider n assets and we denote Ri the rate of return of i-th asset with finite mean value, r = {R1, . . . , Rn}. a discrete probability distribution of rate of returns described by scenarios ri,s, s = 1, . . . , S that are taken with equal probabilities ps = 1/S. a decision maker that may combine the assets into portfolios represented by weights x = {x1, . . . , xn}. the set of feasible weights (no short sales allowed): X = {x ∈ R|

n

  • i=1

xi = 1, xi ≥ 0, i = 1, . . . , n}. (1)

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Second Order Stochastic Dominance

SSD portfolio efficiency

A given portfolio τ ∈ X is SSD portfolio efficient if and only if there exists no portfolio λ ∈ X such that r′λ ≻SSD r′τ. Otherwise, portfolio τ is SSD inefficient. SSD portfolio efficiency tests: Post (2003), Kuosmanen (2004), Kopa and Chovanec (2008)...

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Second Order Stochastic Dominance

Convex second-order stochastic dominance

Fishburn (1974) defines a concept of convex stochastic dominance: We say that portfolio x is convex SSD inefficient if every investor prefers some

  • f the assets to portfolio x.

Formal definition: A given portfolio τ is convex SSD efficient if there exists at least some nondecreasing concave u such that Eu(r′τ) > Eu(ri) for all i = 1, 2, ..., n.

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Second Order Stochastic Dominance

Convex SSD efficiency test

Bawa et al. (1985): Let D = {d1, d2, ..., d(n+1)S} be the set of all scenario returns of the assets and portfolio x, that is, for every i ∈ {1, 2, ..., n + 1} and s ∈ {1, 2, ..., S} exists k ∈ {1, 2, ..., (n + 1)S} such that ri,s = dk and vice versa, where r(n+1),s = n

i=1 ri,sxi.

Convex SSD efficiency test of portfolio x: δ∗(x) = max

δk,xi (n+1)S

  • k=1

δk (2) s.t. F (2)

x

(dk) −

n

  • i=1

¯ xiF (2)

i

(dk) ≥ δk, k = 1, 2, ..., (n + 1)S, δk ≥ 0, k = 1, 2, ..., (n + 1)S, ¯ x ∈ X. A given portfolio x is convex SSD inefficient if δ∗(x) given by (2) is strictly

  • positive. Otherwise, portfolio x is convex SSD efficient.

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Data Envelopment Analysis

Contents

1 Motivation 2 Second Order Stochastic Dominance 3 Data Envelopment Analysis 4 Numerical comparison

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Data Envelopment Analysis

Data Envelopment Analysis (DEA)

Charnes, Cooper and Rhodes (1978): a way how to state efficiency of a decision making unit over all other decision making units with the same structure of inputs and outputs. Let Z1i, . . . , ZKi denote the inputs and Y1i, . . . , YJi denote the outputs of the unit i from n considered units. DEA efficiency of the unit 0 ∈ {1, . . . , n} is then evaluated using the optimal value of the following program where weighted inputs are compared with the weighted outputs. “Are inputs transformed into outputs in an efficient way?”

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Data Envelopment Analysis

Data Envelopment Analysis (DEA)

Charnes et al (1978): fractional programming formulation max J

j=1 yj0Yj0

K

k=1 wk0Zk0

s.t. J

j=1 yj0Yji

K

k=1 wk0Zki

≤ 1, i = 1, . . . , n, wk0 ≥ 0, k = 1, . . . , K, yj0 ≥ 0, j = 1, . . . , J. The unit 0 is then DEA efficient if the optimal value is equal to 1,

  • therwise it is DEA inefficient.

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Data Envelopment Analysis

DEA

Constant Return to Scale (CRS)

Dual problem to linear programming formulation: min θ s.t.

n

  • i=1

xiYji ≥ Yj0, j = 1, . . . , J,

n

  • i=1

xiZki ≤ θ · Zk0, k = 1, . . . , K, xi ≥ 0, i = 1, . . . , n. Model with Constant Return to Scale (CRS).

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Data Envelopment Analysis

DEA

Variable Return to Scale (VRS)

Banker, Charnes and Cooper (1984): DEA model with Variable Return to Scale: min θ s.t.

n

  • i=1

xiYji ≥ Yj0, j = 1, . . . , J,

n

  • i=1

xiZki ≤ θ · Zk0, k = 1, . . . , K,

n

  • i=1

xi = 1, xi ≥ 0, i = 1, . . . , n.

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Data Envelopment Analysis

DEA in finance

Efficiency of mutual funds or financial indexes: Murthi et al (1997): expense ratio, load, turnover, standard deviation and gross return. Basso and Funari (2001, 2003): standard deviation and semideviations, beta coefficient, costs as the inputs, expected return

  • r expected excess return, ethical measure and stochastic dominance

criterion as the outputs. Chen and Lin (2006): Value at Risk and Conditional Value at Risk. Lozano and Guti´ errez (2008): tests consistent with SSD (necessary condition).

  • B. and Kopa (2010, 2012A): VaR, CVaR, sd, lsd, drawdown measures

(DaR, CDaR) as the inputs, gross return as the output; comparison with SSD. Lamb and Tee (2012), B. (2013): DEA tests with diversification.

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Data Envelopment Analysis

Equivalent DEA test to convex SSD efficiency test

Let ˜ D = {d1, d2, ..., d(n+1)S} be the set of all sorted scenario returns of the assets Ri and portfolio x. The test can be rewritten using lower partial moments Li(d) = 1/S S

s=1 [d − ri,s]+.

Based on the results proposed by Bawa et al. (1985)

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Data Envelopment Analysis

Equivalent DEA test to convex SSD efficiency test

  • B. and Kopa (2013): Benchmark portfolio x with return R0 = n

i=1 Rixi.

Find the index ˜ k = arg min{k : L0(dk) > 0}. Then the DEA-risk model with variable return to scale and K = (n + 1)S − 1 inputs δCDEA(R0) = min

¯ xi,ϕ,θk

1 K − ˜ k + 2  

K

  • k=˜

k

θk + 1 ϕ  

n

  • i=1

¯ xiE[Ri] ≥ ϕ · E[R0],

n

  • i=1

¯ xiLi(dk) ≤ θk · L0(dk), k = 1, . . . , K, (3) ≤ θk ≤ 1, ϕ ≥ 1,

n

  • i=1

¯ xi = 1, ¯ xi ≥ 0, i = 1, . . . , n. is equivalent to convex SSD efficiency test.

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Data Envelopment Analysis

Diversification-consistent DEA tests

Input oriented

Recently, general DEA tests with diversification effect were introduced by Lamb and Tee (2012) for a benchmark with return R0: θDC(R0) = min

θ,xi θ

−CVaRεj

n

  • i=1

Rixi

−CVaRεj(−R0), j = 1, . . . , J, (4) CVaR+

αk

n

  • i=1

Rixi

θ · CVaR+

αk(−R0), k = 1, . . . , K, n

  • i=1

xi = 1, xi ≥ 0, i = 1, . . . , n, where CVaR+

α = max{CVaRα, 0}, and αk, εj are different levels, the

positive parts of CVaRs serve as the inputs and expected return as the

  • utput.

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Data Envelopment Analysis

Diversification-consistent test

Input-output oriented I

  • B. and Kopa (2013): Let CVaRα(−R0) > 0 for α ∈ {α1, . . . , αK} and

CVaRε(−R0) < 0 for ε ∈ {ε1, . . . , εJ} θDC I−O I(R0) = min

θ,ϕ,xi

1 K + J

  • θ + 1

ϕ

  • −CVaRεj

n

  • i=1

Rixi

ϕ · (−CVaRεj(−R0)), j = 1, . . . , J, (5) CVaRαk

n

  • i=1

Rixi

θ · CVaRαk(−R0), k = 1, . . . , K, ≤ θ ≤ 1, ϕ ≥ 1,

n

  • i=1

xi = 1, xi ≥ 0, i = 1, . . . , n. Note that CVaR0(−R0) = E[−R0], i.e. expected loss can be also included into this model without any changes in its formulation.

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Data Envelopment Analysis

Diversification-consistent test

Input-output oriented II

  • B. and Kopa (2013):

θDC I−O II(R0) = min

θk,ϕj,xi

1 K + J  

K

  • k=1

θk +

J

  • j=1

1 ϕj   −CVaRεj

n

  • i=1

Rixi

ϕj · (−CVaRεj(−R0)), j = 1, . . . , J, (6) CVaRαk

n

  • i=1

Rixi

θk · CVaRαk(−R0), k = 1, . . . , K, ≤ θk ≤ 1, ϕj ≥ 1,

n

  • i=1

xi = 1, xi ≥ 0, i = 1, . . . , n. These DEA-risk models can be seen as the extension of Russel measure DEA model (see Cook and Seiford (2009)).

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Data Envelopment Analysis

Equivalent DEA test to portfolio SSD efficiency test

  • B. and Kopa (2013): We assume that no CVaRαs of the benchmark is

equal to zero for αs = s/S, s ∈ Γ = {0, 1, . . . , S − 1} Let ˜ s = arg max{s ∈ Γ : CVaRαs(−R0) < 0}, εj ∈ {0/S, 1/S, . . . ,˜ s/S}, J = ˜ s + 1 αk ∈ {(˜ s + 1)/S, . . . , (S − 1)/S}, K = S − ˜ s − 1. Then the corresponding diversification-consistent DEA-risk model (I-O II) is equivalent to SSD portfolio efficiency test, that is, a benchmark R0 = n

i=1 Rixi is DEA-risk efficient if and only if portfolio x is SSD

portfolio efficient. Proof based on Kopa and Chovanec (2008), Ogryczak and Ruszczynski (2002).

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Numerical comparison

Contents

1 Motivation 2 Second Order Stochastic Dominance 3 Data Envelopment Analysis 4 Numerical comparison

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Numerical comparison

Numerical comparison

  • B. and Kopa (2012B,2013): To compare the power of considered efficiency

tests, we consider historical US stock market data, monthly excess returns from January 1982 to December 2011 (360 observations) of 48 representative industry stock portfolios that serve as the base assets. The industry portfolios are based on four-digit SIC codes and are from Kenneth French library. five DEA-risk models where CVaRs at levels α = 0.5, 0.75, 0.9, 0.95, 0.99, 0.995 are used as the inputs and the expected return (the most commonly used reward measure) as the

  • utput.

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Numerical comparison

Traditional Div.-consistent SSD efficiency DEA tests DEA tests VRS CRS I I-O I I-O II convex portfolio Food 1.00 1.00 0.89 0.94 0.89 yes no Beer 1.00 0.92 0.82 0.91 0.82 yes no Smoke 1.00 0.82 1.00 1.00 1.00 yes yes Util 1.00 0.96 0.89 0.88 0.86 yes no

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Numerical comparison

Conclusions

Standard DEA tests can be equivalent to convex stochastic dominance tests. DEA tests equivalent to portfolio stochastic dominance efficiency should take into account diversification effect leading diversification-consistent DEA tests.

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Numerical comparison M.Branda, M.Kopa (Charles University) SP 2013 27 / 32

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Numerical comparison

References

Bawa, V.S., Bodurtha, J.N., Rao, M.R., Suri, H.L. (1985). On Determination of Stochastic Dominance Optimal Sets, Journal of Finance 40, 417–431. Branda, M. (2013). Diversification-consistent data envelopment analysis with general deviation measures, European Journal of Operational Research 226 (3), 626–635. Branda, M., Kopa, M. (2010). DEA-risk efficiency of stock indices. Proceedings of 47th EWGFM meeting, T. Tich´ y and M. Kopa eds., Ostrava: Vˇ SB - Technical University of Ostrava. Branda, M., Kopa, M. (2012A). DEA-Risk Efficiency and Stochastic Dominance Efficiency of Stock Indices, Czech Journal of Economics and Finance 62(2), 106–124. Branda, M., Kopa, M. (2012B). From stochastic dominance to DEA-risk models: portfolio efficiency analysis, In proceeding of international workshop on “Stochastic Programming for Implementation and Advanced Applications”, L. Sakalauskas, A. Tomasgard, S.W. Wallace (Eds.), Vilnius, 13–18. Branda, M., Kopa, M. (2013). On relations between DEA-risk models and stochastic dominance efficiency tests, Central European Journal of Operations Research, available

  • nline. DOI: 10.1007/s10100-012-0283-2

Charnes, A., Cooper, W., Rhodes, E. (1978). Measuring the efficiency of decision-making units, European Journal of Operational Research 2, 429-–444. Chekhlov, A., Uryasev, S., Zabarankin. M. (2003). Portfolio Optimization With Drawdown Constraints, B. Scherer (Ed.) Asset and Liability Management Tools, Risk Books, London.

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Numerical comparison

References

Fishburn, P.C. (1974). Convex stochastic dominance with continuous distribution functions, Journal of Economic Theory 7, 143–158. Hanoch, G., Levy, H. (1969). The Efficient Analysis of Choices Involving Risk, Review of Economic Studies, 335–346. Kopa, M., Chovanec, P. (2008). A Second-order Stochastic Dominance Portfolio Efficiency Measure, Kybernetika 44(2), 243–258. Kuosmanen, T. (2004). Efficient diversification according to stochastic dominance criteria, Management Science 50(10), 1390–1406. Lamb, J.D., Tee, K-H. (2012). Data envelopment analysis models of investment funds, European Journal of Operational Research 216, No. 3, 687–696. Lozano, S., Guti´ errez, E. (2008). Data envelopment analysis of mutual funds based on second-order stochastic dominance, European Journal of Operational Research 189, 230–244. Ogryczak, W., Ruszczynski, A. (2002). Dual stochastic dominance and related mean-risk models, SIAM Journal on Optimization 13, 60–78. Post, T. (2003). Empirical tests for stochastic dominance efficiency, Journal of Finance 58, 1905–1932. Rockafellar, R.T., Uryasev, S. (2000). Optimization of Conditional Value-at-Risk, Journal of Risk, 2, 21–41. Rockafellar, R.T., Uryasev, S. (2002). Conditional Value-at-Risk for General Loss Distributions, J. of Banking and Finance 26, 1443–1471.

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Numerical comparison

Thank you for your attention.

e-mail: branda@karlin.mff.cuni.cz e-mail: kopa@karlin.mff.cuni.cz

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