Efficiency of thin and thick markets

"In this paper, we propose a matching model to study the efficiency of thin and thick markets. Our model shows that the probabilities of matches in a thin market are significantly lower than those in a thick market. When applying our results to a job search model, it implies that, if the ratio of job candidates to job openings remains (roughly) a constant, the probability that a person can find a job is higher in a thick market than in a thin market. We apply our matching model to the U.S. academic market for new PhD economists. Consistent with the prediction of our model, a field of specialization with more job openings and more candidates has a higher probability of matching"--National Bureau of Economic Research web site.