The statistics of industry, labor, and technology give you a good idea of the strength of the Great Powers’ economies.
Industry measures the amount of materials produced by each Great Power over the past several turns, weighted to make more recent turns more important.
Labor is the current total of available labor of each great Power.
Technology measures the number and era of the technologies each country has discovered. You can get details on which power has learned which technology using the small flags on the technology screen itself.