Search theory

This article is about the economics of search problems. For other uses of 'search', see Searching (동음이의).

In microeconomics, search theory studies buyers or sellers who cannot instantly find a trading partner, and must therefore search for a partner prior to transacting.

Search theory has been influential in many areas of economics. It has been applied in labor economics to analyze frictional unemployment resulting from job hunting by workers. In consumer theory, it has been applied to analyze purchasing decisions. From a worker's perspective, an acceptable job would be one that pays a high wage, one that offers desirable benefits, and/or one that offers pleasant and safe working conditions. From a consumer's perspective, a product worth purchasing would have sufficiently high quality, and be offered at a sufficiently low price. In both cases, whether a given job or product is acceptable depends on the searcher's beliefs about the alternatives available in the market.

More precisely, search theory studies an individual's optimal strategy when choosing from a series of potential opportunities of random quality, under the assumption that delaying choice is costly. Search models illustrate how best to balance the cost of delay against the value of the option to try again. Mathematically, search models are optimal stopping problems.

Macroeconomists have extended search theory by studying general equilibrium models in which one or more types of searchers interact. These macroeconomic theories have been called 'matching theory', or 'search and matching theory'.

알려진 분포에서 검색

조지 J 스티글러는 싼 물건이나 일자리를 찾는 것을 경제적으로 중요한 문제로 생각하자고 제안했다.[1][2] John J. McCall은 수학적 최적 중단 방법을 기반으로 한 동적 구직 모델을 제안했는데, 이 모델은 훨씬 이후의 작업에 기초하고 있다.[3][4][5] 맥콜의 논문은 대안의 분포가 알려지고 일정하며 돈의 가치가 일정할 때 실업 노동자가 어떤 직업을 제안하고 어떤 직업을 받아들여야 하는지, 또 어떤 직업을 거부해야 하는지에 대한 문제를 연구했다.[6] 고정된 일자리 특성을 지녔던 그는 구직결정을 예약임금, 즉 노동자가 기꺼이 받아들이려는 최저임금 측면에서 특징지웠다. 근로자의 최적 전략은 단순히 예약 임금보다 낮은 임금 제안을 거부하고, 예약 임금보다 높은 임금 제안을 받아들이는 것이다.

맥콜이 가정한 조건 중 일부가 충족되지 않을 경우, 예약 임금은 시간이 지남에 따라 변경될 수 있다. 예를 들어, 일자리를 찾지 못한 근로자는 기술을 잃거나 오명에 직면할 수 있는데, 이 경우 근로자가 받을 수 있는 잠재적 제안의 분배는 더 나빠질 것이고, 그 또는 그녀는 더 오래 실직 상태에 있게 될 것이다. 이 경우 노동자의 적정예약임금은 시간이 지날수록 감소하게 된다. 마찬가지로 노동자가 위험을 회피하고 있는 경우, 수색 중 점차적으로 돈이 바닥나면 시간이 지날수록 예약임금이 감소한다.[7] 예약임금도 특성이 다른 두 직종에 따라 차이가 있을 것이다. 즉, 직종별로 보상 차이가 있을 것이다.

McCall의 모델에 대한 흥미로운 관찰은 제안의 분산이 커지면 검색자가 더 나은 삶을 살 수 있고, 설사 위험을 회피한다 하더라도 최적의 검색을 연장할 수 있다는 것이다. 임금 제안의 변동(평균을 고정하는 것)이 많을 때, 탐색자는 예외적으로 높은 임금 제안을 받기를 희망하여 더 오래 기다리기를 원할 수 있기 때문이다. 예외적으로 낮은 오퍼를 받을 가능성은 나쁜 오퍼를 거절할 수 있기 때문에 예약 임금에 미치는 영향이 적다.

While McCall framed his theory in terms of the wage search decision of an unemployed worker, similar insights are applicable to a consumer's search for a low price. In that context, the highest price a consumer is willing to pay for a particular good is called the reservation price.

Search from known distributions and heterogeneous costs

Opportunities might provide payoffs from different distributions. Costs of sampling may vary from an opportunity to another. As a result, some opportunities appear more profitable to sample than others. These problems are referred to as Pandora box problems introduced by Martin Weitzman.[8] Boxes have different opening costs. Pandora opens boxes, but will only enjoy the best opportunity. With the payoff she discovered from the box , the cost she has paid to open it and the set of boxes she has opened, Pandora receives

It can be proven Pandora associates to each box a reservation value. Her optimal strategy is to open the boxes by decreasing order of reservation value until the opened box that maximizes her payoff exceed highest reservation value of the remaining boxes. This strategy is referred as the Pandora's rule.

In fact, the Pandora's rule remains the optimal sampling strategy for complex payoff functions. Wojciech Olszewski and Richard Weber[9] show that Pandora's rule is optimal if she maximizes

for continuous, non-negative, non-decreasing, symmetric and submodular.

Endogenizing the price distribution

Studying optimal search from a given distribution of prices led economists to ask why the same good should ever be sold, in equilibrium, at more than one price. After all, this is by definition a violation of the law of one price. However, when buyers do not have perfect information about where to find the lowest price (that is, whenever search is necessary), not all sellers may wish to offer the same price, because there is a trade-off between the frequency and the profitability of their sales. That is, firms may be indifferent between posting a high price (thus selling infrequently, only to those consumers with the highest reservation prices) and a low price (at which they will sell more often, because it will fall below the reservation price of more consumers).[10][11]

Search from an unknown distribution

When the searcher does not even know the distribution of offers, then there is an additional motive for search: by searching longer, more is learned about the range of offers available. Search from one or more unknown distributions is called a multi-armed bandit problem. The name comes from the slang term 'one-armed bandit' for a casino slot machine, and refers to the case in which the only way to learn about the distribution of rewards from a given slot machine is by actually playing that machine. Optimal search strategies for an unknown distribution have been analyzed using allocation indices such as the Gittins index.

Matching theory

Main article: Matching theory (macroeconomics)

More recently, job search, and other types of search, have been incorporated into macroeconomic models, using a framework called 'matching theory'. Peter A. Diamond, Dale Mortensen, and Christopher A. Pissarides won the 2010 Nobel prize in economics for their work on matching theory.[12]

In models of matching in the labor market, two types of search interact. That is, the rate at which new jobs are formed is assumed to depend both on workers' search decisions, and on firms' decisions to open job vacancies. While some matching models include a distribution of different wages,[13] others are simplified by ignoring wage differences, and just imply that workers pass through an unemployment spell of random length before beginning work.[14]

참고 항목

참조

  1. ^ Stigler, George J. (1961). "The economics of information". Journal of Political Economy. 69 (3): 213–225. doi:10.1086/258464. JSTOR 1829263. S2CID 222441709.
  2. ^ Stigler, George J. (1962). "Information in the labor market" (PDF). Journal of Political Economy. 70 (5): 94–105. doi:10.1086/258727. JSTOR 1829106. S2CID 153435494.
  3. ^ Mortensen, D. (1986). "Job search and labor market analysis". In Ashenfelter, O.; Card, D. (eds.). The Handbook of Labor Economics. 2. Amsterdam: North-Holland. ISBN 978-0-444-87857-1.
  4. ^ Lucas, R.; Stokey, N. (1989). Recursive Methods in Economic Dynamics. Cambridge: Harvard University Press. pp. 304–315. ISBN 978-0-674-75096-8.
  5. ^ Adda, J.; Cooper, R. (2003). Dynamic Economics: Quantitative Methods and Applications. Cambridge: MIT Press. p. 257. ISBN 978-0-262-01201-0.
  6. ^ McCall, John J. (1970). "Economics of information and job search". Quarterly Journal of Economics. 84 (1): 113–126. doi:10.2307/1879403. JSTOR 1879403.
  7. ^ Danforth, John P. (1979). "On the role of consumption and decreasing absolute risk aversion in the theory of job search". In Lippman, S. A.; McCall, J. J. (eds.). Studies in the Economics of Search. New York: North-Holland. ISBN 978-0-444-85222-9.
  8. ^ Weitzman, Martin L. (1979). "Optimal Search for the Best Alternative" (PDF). Econometrica. 47 (3): 641–654. doi:10.2307/1910412. hdl:1721.1/31303. JSTOR 1910412.
  9. ^ Olszewski, Wojciech; Weber, Richard (2015-12-01). "A more general Pandora rule?". Journal of Economic Theory. 160 (Supplement C): 429–437. doi:10.1016/j.jet.2015.10.009.
  10. ^ Butters, G. R. (1977). "Equilibrium distributions of sales and advertising prices". Review of Economic Studies. 44 (3): 465–491. doi:10.2307/2296902. JSTOR 2296902.
  11. ^ Burdett, Kenneth; Judd, Kenneth (1983). "Equilibrium price dispersion". Econometrica. 51 (4): 955–969. doi:10.2307/1912045. JSTOR 1912045.
  12. ^ 2010년 경제과학상
  13. ^ Mortensen, Dale; Pissarides, Christopher (1994). "Job creation and job destruction in the theory of unemployment". Review of Economic Studies. 61 (3): 397–415. doi:10.2307/2297896. JSTOR 2297896.
  14. ^ Pissarides, Christopher (2000). Equilibrium Unemployment Theory (2nd ed.). MIT Press. ISBN 978-0-262-16187-9.