Even more fundamental arithmetic lies at the core of the debt quandary. The tax rate required to fund social-welfare benefits depends on three factors: the dependency ratio (the ratio of recipients to taxpayers); the replacement rate (the ratio of benefits to average wages); and the economic-growth rate (roughly, productivity plus population growth).
在债务困境的核心还有更多的基础演算要做。用以支付社会福利补贴的税率取决于三个因素：依赖比率（补贴享受者与纳税人之比）；替代率（补贴与平均工资之比）；经济发展率（大体上是生产力加上人口增长）