Responding to xenophobic concerns, Congress passed an emergency law restricting immigration in 1921. Among other provisions, the Act established a quota (a proportional share of a total) for nationalities on the basis of their numbers in the U.S. in 1910.
The missing detail is: a quota.
I believe it was the Radio
Answer:
Over and above being bitten, mauled, trampled, trodden, crushed, kicked, gouged, horned, spindled and mutilated by our domestic friends, we also have accepted them into our midst at the risk of other aspects of our health. They have brought to us a variety of diseases.
One reason that more people didn’t foresee the economic collapse of the 1930s is that it came about so suddenly, with practically no warning, since the US economy throughout the 20s was thriving and "booming"--leading people to think that there were no issues whatsoever.
