This has two effects. 1. People who stay, actually want to stay. Massively improving the stability of the community. 2. The outside communities receive a fresh infusion of population, that's already well integrated into the society, rather than refugees coming from 10000 miles away.
Essentially, rural america will eventually be different shades of Amish (in about 100 years). The amish population will overflow from the farms, and flow into the cities, replenishing the population of the more productive cities (Which are not population-self-sustaining).
This is a sustainable arrangement, and eliminates the need of mass-immigration and demographic destabilisation. This is also in-line with historical patterns, cities have always had negative natural population growth (disease/higher real estate costs). Cities basically grind population into money, so they need rural areas to replenish the population.
That depends on how you define "want".
Amish are ostracized by their family and community if they leave. That's some massive coercion right there: either stay or lose your connection to the people you're closest to and everything you've ever known and raised to believe your whole life.
Not much of a choice, though some exceptionally independent people do manage to make that sacrifice.
I had not heard this before. Do you have citations for this?
(I realize cities have lower birth rate than rural areas in many cases. I am interested in the assertion that they are negative. Has it always been so? Or have cities and rural areas declined at same rate?)
The actual counter to fertility decline, may be AI teachers. AI will radically close the education gap between rich and poor, and lower the costs. All you need is a physical human to supervise the kid, the AI will do the rest, from entertainment, to education, to identifying when the child is hungry/sleepy/potty, and relaying that info for the human to act on.