The Financial Times reports that a Chinese government crackdown on the sale of data from its sprawling statistics agencies has prompted a marked deterioration in the numbers that investors rely on to understand the world’s second-largest economy. Executives searching for figures on China’s petroleum exports or wind power output have noticed growing gaps in the numbers, with some data released later or missing entirely. That has made it harder to assess the state of the broader economy and the many industries in which the country has become the dominant producer or buyer of raw materials. The gaps appeared after the Central Central Committee for Disciplinary Inspection began a probe into the National Bureau of Statistics six months ago.