The temptation is all too strong. How many bureaucrats would work just as hard to show that their department was less important, less necessary, and less deserving of funding? It’s the fatal trap of socialist management. The incentives are wrong.

When governments are faced with poor reports, but they write their own report cards, they have many options to upgrade their “score”. It’s insane to think that people might not take every opportunity they can to improve their mark. They are human.

Big problems like inflation, unemployment, national growth, or global temperatures can be “improved” two ways –one way takes tough decisions and years of work, and the other way takes a quiet statistical summit, a white paper and an in-house training weekend. It’s easier to “solve” big problems by changing the way you measure them. By changing definitions, methods of interpreting the data, or through sheer statistical chicanery it’s possible to issue press releases with the words “improvement”, “better than expected” or at least “figures have plateaued”.

For example, the inflation of the 1970s was partly “cured” by defining inflation as the consumer price index (CPI), then changing the way that [...]