Approval Rating - Ratio of happy to unhappy people
GNP - Income based on trade and tax/luxury rates
Since it is based on the tax slider, it can't be your total commerce "production" (total income). It is the part of your total commerce income that goes to taxes instead of science or luxury. I don't know however if buildings and military upkeep is deducted or not to get the final sum.
Manufactured goods - Total number of shields
Family size - Based on average food surplus
Military Service - Number of military units in relation to population
Productivity - Shields per total squares inside your borders (in civ2 it was shields minus support per square in use so I guessed that now it must be squares inside your borders)
I think this was on this site somewhere and I saved it.