STEERING AN economy has never been easy. In a candid(坦诚的，直率的) presentation in 1975 Charles Goodhart, then of the Bank of England, shared some of Britain’s “unhappy” experiences after sterling lost its link to(与……失去联系，脱钩) the dollar four years before. Instead of defending an exchange rate, the bank had hoped to use interest rates to control the supply of money, variously(以不同方式，在不同方面) measured. But the monetary authorities had ignored what the presenter playfully called Goodhart’s law: “Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.”(但货币当局忽视了演讲者戏称的古德哈特定律：“任何观察到的统计规律，一旦被施加压力用于控制目的，就会趋于崩溃。”)
驾驭经济从来都不是一件容易的事。在1975年的一次坦诚演讲中，时任英国央行官员的查尔斯·古德哈特分享了英镑在四年前与美元脱钩后英国的一些“不愉快”经历。英国央行当时希望用利率来控制货币供应量（以不同方式衡量），而不是捍卫汇率。但货币当局忽视了演讲者戏称为“古德哈特定律”的现象：“一旦对某种统计规律施加压力用于控制目的，它往往会失效。”
Others have put this more snappily(更简洁地表达这一点): when a measure becomes a target, it ceases to be a good measure. The law poses particular difficulties for China, which has many economic targets and thus few good measures. In 2018, for example, it began publishing a new monthly gauge(测量标准，指标) of urban unemployment, based, like similar statistics elsewhere, on surveys of the population. But unlike other countries’ figures, China’s measure has remained remarkably(显著地，异常地) stable. July’s rate of 5.2%, published on August 17th, was typical. It was less than 6% but at least 5% for the 99th time in the past 115 months. Even during the covid-19 pandemic, when American unemployment climbed well into double digits, China’s measure never exceeded 6.2%.(即使在新冠疫情期间，当美国失业率攀升至两位数时，中国的指标也从未超过6.2%。)
其他人更简洁地表述为：当一个指标成为目标时，它就不再是一个好指标。这条定律给中国带来了特别的困难，因为中国有许多经济目标，因此很少有好的指标。例如，2018年，中国开始发布一个新的月度城镇失业率指标，与其他地方的类似统计一样，基于人口调查。但与其他国家的数据不同，中国的指标一直保持异常稳定。7月份公布的5.2%的失业率就很典型。在过去115个月中，有99次低于6%但至少为5%。即使在新冠疫情期间，当美国失业率攀升至两位数时，中国的指标也从未超过6.2%。
One reason may be that the survey covers only urban workers. The flow of migrants into and out of China’s cities gives the urban labour market a homoeostatic(自我平衡的，稳态的) quality. When job creation is strong and the unemployment rate is set to fall, more of them turn up, expanding the denominator.(当就业创造强劲、失业率趋于下降时，会有更多移民涌入城市，从而扩大分母。) Conversely, when the labour market is weak, the jobless seek work in the countryside, dropping out of(退出，脱离) the survey.
一个原因可能是该调查只覆盖城镇工人。移民进出中国城市的流动赋予了城镇劳动力市场一种自我平衡的特性。当就业创造强劲、失业率趋于下降时，会有更多移民涌入城市，从而扩大分母。相反，当劳动力市场疲软时，失业者会去农村找工作，从而退出调查。
