Move to "a place principally because of job opportunities". I'm saying that 1-income households can do that. They can go anywhere affordable even if there is o

Move to "a place principally because of job opportunities". I'm saying that 1-income households can do that. They can go anywhere affordable even if there is only 1 employer with 1 opening. The 2-income households, with notably different culture, can't move unless they find a pair of jobs. Finding a pair of jobs is far easier in a large city. There are plenty of jobs outside the large cities, possibly even most jobs depending on your definition of "large city", but they are too far spread out to select the location first. You select a job, and that may take you somewhere rural. If you first select a specific rural location, you are unlikely to find a job. So for one culture, with the single-income family, it is no big deal to move for a job. If that fails, you move again. For the other culture, with two incomes, you have to move to a place that has a high probability of having jobs for both people whenever that is needed. Moving is less of an option.