Browsing by Author "Doğan, B."

Now showing 1 - 6 of 6

Open Access
Choice with affirmative action
(Institute for Operations Research and the Management Sciences (INFORMS), 2022-02-09) Doğan, B.; Yıldız, Kemal
A choice rule with affirmative action decides on the recipients of a limited number of identical objects by reconciling two objectives: respecting a priority ordering over the applicants and supporting a minority group. We extend the standard formulation of a choice problem by incorporating a type function and a priority ordering, and introduce monotonicity axioms on how a choice rule should respond to variations in these parameters. We show that monotonic and substitutable affirmative action rules are the ones that admit a bounded reserve representation. As a prominent class of choice rules that satisfy the monotonicity axioms, we characterize lexicographic affirmative action rules that are prevalent both in the literature and in practice. Our axiomatic approach provides a novel way to think about reserve systems and uncovers choice rules that go beyond lexicographic affirmative action rules.
Open Access
Efficiency and stability of probabilistic assignments in marriage problems
(Academic Press, 2016) Doğan, B.; Yıldız, K.
We study marriage problems where two groups of agents, men and women, match each other and probabilistic assignments are possible. When only ordinal preferences are observable, stochastic dominance efficiency (sd-efficiency) is commonly used. First, we provide a characterization of sd-efficient allocations in terms of a property of an order relation defined on the set of man-woman pairs. Then, using this characterization, we constructively prove that for each probabilistic assignment that is sd-efficient for some ordinal preferences, there is a von Neumann-Morgenstern utility profile consistent with the ordinal preferences for which the assignment is Pareto efficient. Second, we show that when the preferences are strict, for each ordinal preference profile and each ex-post stable probabilistic assignment, there is a von Neumann-Morgenstern utility profile, consistent with the ordinal preferences, for which the assignment belongs to the core of the associated transferable utility game. © 2015 Elsevier Inc.
Open Access
Lexicographic choice under variable capacity constraints
(Wiley, 2021) Doğan, B.; Doğan, Serhat; Yıldız, Kemal
In several matching markets, to achieve diversity, agents' priorities are allowed to vary across an institution's available seats, and the institution is let to choose agents in a lexicographic fashion based on a predetermined ordering of the seats, called a (capacity-constrained) lexicographic choice rule. We provide a characterization of lexicographic choice rules and a characterization of deferred acceptance mechanisms that operate based on a lexicographic choice structure under variable capacity constraints. We discuss some implications for the Boston school choice system and show that our analysis can be helpful in applications to select among plausible choice rules.
Open Access
A new ex-ante efficiency criterion and implications for the probabilistic serial mechanism
(Academic Press, 2018) Doğan, B.; Doğan, Serhat; Yıldız, Kemal
We introduce and analyze an efficiency criterion for probabilistic assignment of objects, when only ordinal preference information is available. This efficiency criterion is based on the following domination relation: a probabilistic assignment dominates another assignment if it is ex-ante efficient for a strictly larger set of utility profiles consistent with the ordinal preferences. We provide a simple characterization of this domination relation. We revisit an extensively studied assignment mechanism, the Probabilistic Serial mechanism (Bogomolnaia and Moulin, 2001), which always chooses a “fair” assignment. We show that the Probabilistic Serial assignment may be dominated by another fair assignment. We provide conditions under which the serial assignment is undominated among fair assignments.
Open Access
Rethinking interest rate volatility as a macroprudential policy tool
(Routledge, 2016) Doğan, B.; Şahin, A.; Berument, Hakan
Along with most other central banks, Turkey’s central bank has implemented unconventional policies since the 2007/2008 financial crisis. Financial stability has been one of the targets of these macroprudential policies. However, since Turkey is working toward this goal without increasing its inflation rate, tracking only short-term interest rates to measure this policy’s effectiveness would be inefficient. In this paper, we provide empirical evidence from Turkey that interbank interest rate volatility can be an additional tool for monetary policy makers to help achieve the goal of financial stability. Impulse responses generated from the Vector Autoregressive models indicate that interest rate volatility increases interest rates, depreciates domestic currency and decreases credit growth and output. Its statistically insignificant effect on prices is open to interpretation.
Open Access
Three-factor asset pricing model and portfolio holdings of foreign investors: evidence from an emerging market–Borsa Istanbul
(Routledge, 2015-08-27) Ceylan, N. B.; Doğan, B.; Berument, Hakan
This article contributes to the asset pricing literature by offering an alternative missing factor: the excess holdings of foreign investors. To incorporate this factor, we mimic the portfolio of foreign investors in Borsa Istanbul (BIST) with respect to portfolio preferences (foreign ownership) using the Fama and French’s three-factor model. Our findings suggest that market factor, size, and book-to-market (B/M) variables are still statistically significant and Jensen’s alpha is still not significant, and we obtain a statistically significant negative relationship between the excess return of foreign investors’ ownership and the return variation of a given portfolio.