The only other thing I could find out is that the 50 variables are grouped into the following categories:

* Trade policy,
* Fiscal burden of government,
* Government intervention in the economy,
* Monetary policy,
* Capital flows and foreign investment,
* Banking and finance,
* Wages and prices,
* Property rights,
* Regulation, and
* Informal market activity.

I have to guess that the US really bombed some to make up for the fact that Britain is surely below us in property rights, wages and prices. Might be worth taking a look at the full report.