With the closing of the frontier and static populations, growth would depend on innovation; but future innovation would require smaller inputs of capital and labor than in the past. In other words, the returns to capital were bound to fall as it became more abundant relative to population.
随着西进空间的缩减和人口趋势的稳定，增长将依赖创新；但未来创新所需要的资本和劳动力投入比过去要小。换句话说，随着资本相对人口变得富于，资本回报必然会下降。在这样的环境下，充分就业唯有通过持续的财政赤字才能维持。