Macroeconomic models have tended to neglect the role of institutions, ranging from trade unions and employer associations to property-rights regimes and mechanisms for redistribution. Taking them seriously means considering long historical intervals, because institutions change slowly and vary significantly only over time.
这一“不同时间和地点”的定语触及到新实证研究的第四个也是最后一个重点：制度。宏观经济模型总是忽略制度的作用——不管是工会、雇主联盟还是产权制度和再分配机制。认真处理这些因素意味着考察长期历史时期，因为制度的演变十分缓慢，并且只能随着时间的推移发生重大变化。因此，重新关注历史让经济学家可以更系统地考察制度对宏观经济结果的作用。