One never knows, for example, when rising debt levels might alarm international investors, who then start demanding sharply higher interest rates, as happened to countries on the European periphery in 2010. We are also uncertain about the magnitude of the negative long-term effects of high tax rates on growth.
当然，财政政策的效果是不确定的。比如说，没有人会知道增加债务水平何时会使国际投资者受惊并开始追求高利率——一如2010年发生在欧洲外围国家的情况一样。同时我们也不能确定高税率对经济增长的长期消极影响有多大。而人们对货币政策的理解比以前要好得多。确实，一份备受推崇的新报告把货币政策描述为科学，而财政政策则更像炼金术。