Why are some countries richer than the others? Which is the main reason—is it the abundance of natural resources; or the supply of the highly educated labor force (human capital); or political and...

Why are some countries richer than the others? Which is the main reason—is it the abundance of natural resources; or the supply of the highly educated labor force (human capital); or political and social l harmony (ie, lack ethnic conflict); or just the continuous stream of new technology?