"Imagine how much worse off the country might be if the 49ers had decided against making the trek to California or the sharecroppers chose to stay in the South."
I'm assuming by '49ers' he means the gold rush of 1849, many of whom took a chance on coming out to the west to try and find gold. But sharecroppers?
Sharecroppers didn't "choose" to move away from the south. They were basically poor uneducated people without any other form of work available to them. A good portion of them were the direct descendents of slaves who used to work the same land in the same way. They lost their indentured servitude when they became obsoleted by the mechanization of farming. There were no other jobs in the area, but as luck would have it, a big push for more industrial workers was happening in the north and west.
That's not some kind of "admirable trait". They had no choice but to go find work elsewhere, and were lucky to find it. You don't have to be an economist to figure out that today, people aren't going to be spending lots of money they don't have to move around the country for jobs that don't exist.
We live in a global marketplace now, and almost all of our exports are things machines assemble for us. Unskilled labor is shrinking fast. Our economy is weak. Our government is hobbled. Our education sucks. Our healthcare gets exponentially more expensive. The only incentive I can think of to move is for educated people to move toward centers of white-collar business for the remaining and new jobs, and maybe gentrification away from expensive metropolises people can no longer afford.
So yeah, NYT, we're not going anywhere.