按风险现金流实际利率的通常水平5%计算，在今年将如此大比重的资源从直接可用的商品和服务中抽出，如果要让其不至于得不偿失，就意味着这笔资源能够提振0.3%的年经济增长 — — 或在25年的一代人的时间里提振6 % 。
At a typical 5% annual real interest rate for risky cash flows, diverting that large a share of resources away from goods and services directly useful this year is a good bargain only if it boosts overall annual economic growth by 0.3% – or 6% per 25-year generation.