He explained that it would soon be possible to build a mathematical model that would accurately predict the future course of the economy. It was but a step from there to realize that the problems of policymaking would soon be over.
All it would take was a bit of algebra to solve for the policies that would produce the desired values of the target variables. It was a wonderful prospect, and it remains a wonderful idea. But it has not yet happened. I want to talk about why not and about some of the consequences for policymaking.