What other data do you think we could look at to us gauge a country’s level of development? why would it ?

GDP, which we use right now, to see how many people have jobs, at what income, to decide how good the economy is. We could possibly use population density, as poorer countries/less developed countries tend to be more dense all around. Mainly economic things though, so GDP, income per capita. We use life expectancy, rate of literacy, freedom index..hope this helps