It's more like a pyramid, where the people at the top of the pyramid go farther up the more people you add to the bottom. The size of the whole pyramid increase

It's more like a pyramid, where the people at the top of the pyramid go farther up the more people you add to the bottom. The size of the whole pyramid increases over time, and some people might move up or down a few levels, but the majority of people will spend their whole lives near the bottom.