Summers emphasizes the inadequacy of aggregate demand, exacerbated by the inability of central banks to reduce nominal interest rates below zero. The reasons for weak aggregate demand include aging populations that consume less and the growing concentration of wealth among the very rich, whose marginal propensity to consume is small.
这一停滞的原因在很大程度上取决于经济学家之所指。萨默斯强调总需求的不足，这一不足因为中央银行无法将名义利率降至零以下而加剧。总需求萎靡的原因包括人口老龄化导致消费减少和财富日渐向边际消费倾向很低的巨富集中。