Notable exceptions are the seminal paper by Lazear (1990), as well as Scarpetta (1996), Elmeskov et al. ( More recently, some studies have exploited the fact that certain EPL reforms were targeted on specific groups of workers or firms or were undertaken at different times in different states or regions, thereby generating quasi-natural experiments. For example, there is a growing literature looking at the labour market effects of increasingly frequent exceptions to the employment-at-will doctrine in the United States, which were adopted in different years by courts of different states.