Suppose that the US government were to borrow an extra $500 billion over the next two years and spend it on infrastructure – even unproductively, on projects for which the social rate of return is a measly 25% per year. Suppose that – as seems to be the case – the simple Keynesian government-expenditure multiplier on this spending is only two.
当前，美国政府的30年债务真实（经通胀调整的）利率为每年1%。假设未来两年美国政府多借5000亿美元，并将这笔钱用于基础设施建设——即使这些投资并非生产性的，其社会回报率只有每年25%。假设——目前看来正是如此——简单凯恩斯政府支出乘数 为2。