A Rule of Thumb on Immigration
Nativists occasionally assert that a high rate of immigration is an unprecedented experiment. On the other hand, the US immigration in 1907 was 1.5% of the population. So … maybe we can admit up to 1.5% of the population each year. That's more than the current rate of immigration to Europe during this refugee “crisis.”
A potential problem: The above rule of thumb implies that the 2003 Iraq invasion was the 2003 Iraq immigration. This is oddly low for a successful invasion.