I think it's partly censorship, and partly the secrecy around the creation of economic (and other) data. When people are incentivised to report inaccurate data

I think it's partly censorship, and partly the secrecy around the creation of economic (and other) data. When people are incentivised to report inaccurate data and have the ability to do so, they will. This is an old problem. Emperor Kangxi developed a secret palace memorial system in the seventeenth century to learn from trusted eunuchs if the grain prices his senior officials were reporting were accurate, and if his son was a monster, and things like that.