GDP is an excellent example, I think. Basically, it measures the total flow of wealth inside a country. If everyone behaves rationally this is a good proxy for

GDP is an excellent example, I think. Basically, it measures the total flow of wealth inside a country. If everyone behaves rationally this is a good proxy for wealth as a whole. But what happens if the government would setup a group of companies that trade immaterial or trivial products amongst each other at absurd prices? The faster that group trades, the higher the GDP. A metric has become a goal.