遗憾的是，世行的指数仍受限于数据不足以及经济学家理解上的欠缺。例如，发育迟缓和生产率之间存在怎样的关联仍旧很难说清。全世界只有65%的出生人口办理了登记，登记在册的死亡则只有38%。许多国家即使会对学生展开测验，也并不经常举行。如果一国的学生直到15岁才接受测试，那么在这些孩子长到足够的年龄、在测试中取得了好成绩之前，任何帮助小学生学习的改革都不会提升该国的排名。Unfortunately the index is still hobbled by gaps in the data and in economists’ understanding. The link between stunting and productivity, for example, remains murky. Only 65% of the world’s births are registered, as are only 38% of deaths. Many countries test their schoolchildren infrequently, if at all. If pupils are not tested until the age of 15, then any reform that helps primary-schoolers learn will not improve the country’s ranking until they grow old enough to ace the tests.
世行本身已提示数据存在缺陷。它希望这个指数的存在会激励各国政府去收集让指数正确发挥作用所需的数据。化用下麦克洛斯基喜欢的另一个比方，可以说世行造出了一辆拉风的跑车，现在它得激起各国政府的羞愧感，好让它们去修配得上这辆车的路。The World Bank has itself flagged these data shortcomings. It hopes the very existence of its index will motivate governments to collect the data the index needs if it is to work properly. To adapt another metaphor favoured by Ms McCloskey, the World Bank has built a sleek sports car; now it must shame governments into building roads that are worthy of it.