Umut Keskin - Academia.edu (original) (raw)

Papers by Umut Keskin

Social Choice and Welfare, 2022

Driven by the exponential growth in computing power and the digitization of things, artificial in... more Driven by the exponential growth in computing power and the digitization of things, artificial intelligence (AI) and robotics are poised to transform the economy. While these technologies are likely to boost productivity and generate significant wealth, their potential impact on the labour market is concerning, with some estimates suggesting that nearly half of all existing jobs could be automated in the next two decades. What is almost certain is that these technologies will further increase inequality: workers with skills that are complementary to these new technologies will benefit, while those with skills that are substitutes will face dimming job prospects. The extent and speed of the transformation remains uncertain. This paper presents several possible scenarios for the future of work and draws on the Industrial Revolution to offer a historical perspective. It ends with a discussion of different policy options that could be deployed. Foremost, it highlights the urgent need for further international collaboration to broaden the tax base, both because tax avoidance is likely to become a bigger problem as wealth and income become increasingly concentrated and mobile and because of the likely need to expand the social safety net in the face of potentially massive and long-lasting disruptions.

markdownabstractBeing labeled as a social science, much of economics is about understanding human... more markdownabstractBeing labeled as a social science, much of economics is about understanding human behavior; be it in the face of uncertainty or delayed payoffs through time or strategic situations such as auctions, bargaining, and so on. This thesis will be concerned with the first two, namely uncertainty and time preferences. The main focus of this thesis is what we can summarize with two broad titles: "irrationalities" in human behavior and an alternative perspective on 'rational behavior". My claim requires a clarification of what is meant by rational or irrational behavior. In one of the early discussions of this topic, Richter (1966) defined a rational consumer as someone for whom there exists a total, reflexive, and transitive binary relation on the set of commodities so that his choice data consists of maximal elements of this binary relation. In this respect, Richter (1966) only imposed minimal consistency conditions on behavior for it to be labeled as rat...

Social Choice and Welfare, 2020

A social choice rule (SCR) is monotonic if raising a single alternative in voters' preferences wh... more A social choice rule (SCR) is monotonic if raising a single alternative in voters' preferences while leaving the rankings otherwise unchanged is never detrimental to the prospects for winning of the raised alternative. Monotonicity is rather weak but well-known to discriminate against scoring elimination rules, such as plurality with a run o and single transferable vote. We dene the minimal monotonic extension of an SCR as its unique monotonic supercorrespondence that is minimal with respect to set inclusion. After showing the existence of the concept, we characterize, for every non-monotonic SCR, the alternatives that its minimal monotonic extension must contain. As minimal monotonic extensions can entail coarse SCRs, we address the possibility of rening them without violating monotonicity provided that this renement does not diverge from the original SCR more than the divergence prescribed by the minimal monotonic extension itself. We call these renements monotonic adjustments and identify conditions over SCRs that ensure unique monotonic adjustments that are minimal with respect to set inclusion. As an application of our general ndings, we consider plurality with a runo, characterize its minimal monotonic extension as well as its (unique) minimal monotonic adjustment. Interestingly, this adjustment is not coarser than plurality with a runo itself, hence we suggest it as a monotonic substitute to plurality with a runo. JEL Classications: D71, D79.

Economics Letters, 2020

This paper uses Gilboa’s (1989) variation aversion model to examine additive separability in inte... more This paper uses Gilboa’s (1989) variation aversion model to examine additive separability in intertemporal decision models. We present a characterization of this model using present values and based on this characterization, we argue that additive separability may not necessarily be rational in some settings. Our method also has the advantage that it allows for testing models by using econometric techniques.

Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017), 2017

Simulation of horizontal tau-neutrino induced shower to optimize the site parameters A .YILMAZ

Management Science, 2017

This paper studies the effect of learning information on people's attitudes towards ambiguity. We... more This paper studies the effect of learning information on people's attitudes towards ambiguity. We propose a method to separate ambiguity attitudes from subjective probabilities and to decompose ambiguity attitudes into two components. Under models like prospect theory that represent ambiguity through nonadditive decision weights these components reflect pessimism and likelihood insensitivity. Under multiple priors models, they reflect ambiguity aversion and perceived ambiguity. We apply our method in an experiment where we elicit the ask prices of options with payoffs depending on the returns of initial public offerings (IPOs) on the New York Stock Exchange. IPOs are a natural context to study the effect of learning, as prior information about their returns is unavailable. Subjects perceived substantial ambiguity and they were insensitive to likelihood information. We observed only little pessimism and ambiguity aversion. Subjective probabilities were well-calibrated and close to the true frequencies. Subjects' behavior moved towards expected utility with more information, but substantial deviations remained even in the maximum information condition.

Economics Working Paper Archive, Aug 1, 2013

This paper studies the effect of learning new information on decision under uncertainty. Using am... more This paper studies the effect of learning new information on decision under uncertainty. Using ambiguity models, we show the effect of learning on beliefs and ambiguity attitudes. We develop a new method to correct beliefs for ambiguity attitudes and decompose ambiguity attitudes into pessimism (capturing ambiguity aversion) and likelihood insensitivity. We apply our method in an experiment using initial public offerings (IPOs) on the New York Stock Exchange. IPOs provide a natural decision context in which no prior information on returns is available. We found that likelihood insensitivity decreased with information, but pessimism was unaffected. Subjects moved in the direction of expected utility with more information, but significant deviations remained. Subjective probabilities, corrected for ambiguity attitudes, were well calibrated and close to market data.

Advanced Maui Optical and Space Surveillance Technologies Conference, 2007

Atmospheric turbulence degrades the resolution of images of space objects beyond that predicted b... more Atmospheric turbulence degrades the resolution of images of space objects beyond that predicted by diffraction alone. Adaptive optics telescopes have been widely used for compensating these effects, but as users seek to extend the envelopes of operation of adaptive optics telescopes to more demanding conditions, such as daylight operation and operation at low elevation angles, the level of compensation provided will degrade. We have been investigating the use of advanced wave front reconstructors and post detection image reconstruction to overcome the effects of turbulence on imaging systems in these more demanding scenarios. In this paper we show results comparing the optical performance of the exponential reconstructor, the least squares reconstructor, and the stochastic parallel gradient descent algorithm in a closed loop adaptive optics system using a conventional continuous facesheet deformable mirror and a Hartmann sensor. The performance of these reconstructors has been evaluated under a range of source visual magnitudes, and zenith angles up to 67 degrees. We have also simulated satellite images, and applied speckle imaging, multiframe blind deconvolution algorithms, and deconvolution algorithms that presume the average point spread function is known to compute object estimates.

The Advanced Maui Optical and Space Surveillance Technologies Conference, 2006

The problem of mitigating atmospheric turbulence-induced distortions from imagery measured by ast... more The problem of mitigating atmospheric turbulence-induced distortions from imagery measured by astronomical and space surveillance telescopes operating at high zenith angles is addressed here. Most previous research in this problem has emphasized operation at relatively small zenith angles, where turbulence effects are less severe, and effects arising from relatively weak phase distortions dominate the measurements. As the zenith angle increases the propagation path through the atmosphere gets progressively longer, with the result that the wave front arriving at the telescope is corrupted by both phase and amplitude fluctuations. This poses a problem for conventional adaptive optics systems because the assumptions implicit to their design and construction are violated. Our goal is to examine and compare the performance of two approaches to deformable mirror control a conventional recursive technique, and the slope discrepancy technique. We created a closed loop adaptive optics imaging simulation of an AEOS-like adaptive optics system imaging a star at zenith angles in the range 0-70 degrees using both deformable mirror control paradigms, and compare performance. Our results show that the slope discrepancy wave front reconstructor provides significantly better performance at all zenith angles, but this performance advantage is particularly strong at high zenith angles.

Operations Research, 2015

We introduce a new type of preference condition for intertemporal choice, which requires present ... more We introduce a new type of preference condition for intertemporal choice, which requires present values to be independent of various other variables. The new conditions are more concise and more transparent than traditional ones. They are directly related to applications because present values are widely used tools in intertemporal choice. Our conditions give more general behavioral axiomatizations, which facilitate normative debates and empirical tests of time inconsistencies and related phenomena. Like other preference conditions, our conditions can be tested qualitatively. Unlike other preference conditions, our conditions can also be directly tested quantitatively, and we can verify the required independence of present values from predictors in regressions. We show how similar types of preference conditions, imposing independence conditions between directly observable quantities, can be developed for decision contexts other than intertemporal choice and can simplify behavioral axiomatizations there. Our preference conditions are especially efficient if several types of aggregation are relevant because we can handle them in one stroke. We thus give an efficient axiomatization of a market pricing system that is (i) arbitrage-free for hedging uncertainties and (ii) time consistent.

Optical Engineering, 2014

The potential benefits of real-time, or near-real-time, image processing hardware to correct for ... more The potential benefits of real-time, or near-real-time, image processing hardware to correct for turbulence-induced image defects for long-range surveillance and weapons targeting are sufficient to motivate significant resource commitment to their development. Quantitative comparisons between potential candidates are necessary to decide on a preferred processing algorithm. We begin by comparing the mean-square-error (MSE) performance of speckle imaging (SI) methods and multiframe blind deconvolution (MFBD), applied to long-path horizontal imaging of a static scene under anisoplanatic seeing conditions. Both methods are used to reconstruct a scene from three sets of 1000 simulated images featuring low, moderate, and severe turbulence-induced aberrations. The comparison shows that SI techniques can reduce the MSE up to 47%, using 15 input frames under daytime conditions. The MFBD method provides up to 40% improvement in MSE under the same conditions. The performance comparison is repeated under three diminishing light conditions, 30, 15, 8 photons per pixel on average, where improvements of up to 39% can be achieved using SI methods with 25 input frames, and up to 38% for the MFBD method using 150 input frames. The MFBD estimator is applied to three sets of field data and representative results presented. Finally, the performance of a hybrid bispectrum-MFBD estimator that uses a rapid bispectrum estimate as the starting point for the MFBD image reconstruction algorithm is examined.

Radiation Physics and Chemistry (1977), 1983

Gamma and electron radiation effects on wheat straw, oat straw, barley straw and rye straw are re... more Gamma and electron radiation effects on wheat straw, oat straw, barley straw and rye straw are reported. In vitro and in viva studies show that the digestibility of these allricultural rough materials can be increased up to 80c~ and more at high doses. The increase of the digestibility is connected with a depolymerisation of cellulose and hemicellulose.