"Most empirical policy work requires the aggregation of policies. Trade policy aggregation exemplifies the aggregation problem poignantly, with thousands of highly dispersed trade barriers. This paper provides methods of policy aggregation that are consistent with two common objectives of empirical work. One is to preserve real income. The other is to preserve the real volume of activity in the parts of the economy being aggregated. Both objectives must be achieved for consistent multi-country policy modeling. An application to India shows that the standard atheoretic method of aggregation overstates India's real income by around 3 times the global gains from free trade"--National Bureau of Economic Research web site.