It’s a trend that’s a few centuries old at least. The French and Indian War was partly caused by Americans who didn’t have enough land to farm to support a family moving west, and the British trying to stop that was one cause of the Revolution, and then the whole of 19th century American history is a combination of farmers moving west because the east was full and immigration from Europe largely driven by the farmland of Europe being full. Before that almost everywhere was stuck in a Malthusian equilibrium and if you couldn’t support a family in your home, moving away would just make it harder.
