Introductory textbooks once taught that raising the minimum wage must reduce employment: if labor grows more expensive, firms will hire fewer workers. A wave of empirical studies beginning in the 1990s challenged this certainty. Comparing neighboring regions where one raised its wage floor and the other did not, several economists found little or no fall in employment, and sometimes a slight rise. Various explanations followed. Some argued that employers in many local labor markets hold enough wage-setting power that a modest mandated increase simply trims that power without cutting jobs. Others noted that better-paid workers quit less often, lowering the costs of turnover and training. Skeptics reply that the studies examine only modest increases over short periods, and warn that a steep hike could still cost jobs. The dispute has narrowed the question from whether minimum wages reduce employment to how large an increase a given labor market can absorb.