Each generation gets the opportunity to rule the world. Because it's always someone's turn to rule the world. If the generation begins ruling early, then those who participate have time to make a lot of changes. If the next generation is not loud enough, or not rich enough, or not aggressive enough, then their rule is short, passed to them through the right of mortality. The earth turns the same speed, but it seems to go a little slower for the latecomers.
There is just a fraction of any one generation that takes initiative to lead. The fraction becomes the voice or their generation, whether the masses agree with them or not, or just partially. Most likely it is partially. Enough to not oppose. Enough to buy the books and see the movies, if for no other reason than for curiosities sake.
The masses of any one generation give enough support through lack of resistance to have their lives spoken for. Their standard of living is set at a base level, it is up to each individual to better it, their access to services and resources is again set to a base, and it is again up to each individual to better their access.
The leaders of the masses know one thing, and that is to keep the masses divided. In division the masses can be corralled into manipulated movements designed for specific, time sensitive issues. Those movements can be broken and reorganized at another time. Only a few out of millions have to participate.
The dynamics of the divisions change with the change of leadership. New generations bring on different crowd dynamics, and thus different manipulative tactics from leadership.
Knowing the crowd dynamics of a rising generation will give keen insight into the structure of future political systems.