How did america change in the 1930s? what caused this change ?

Which of these number is main idea? i need . (1) the health-care field is now a stable middle-class career path for a number of americans, especially women. (2) "we used to think about the men going out with their lunch bucket to their factory, and those were good jobs," said jane waldfogel, a professor at columbia university who studies work and family issues. (3) "what's the corresponding job today? (4) it's in the health-care sector." (5) in 1980, 1.4 million jobs in health care paid a middle-class wage; today, the figure is 4.5 million. (6) the pay of registered nurses—now the third-largest middle-income occupation and one that continues to be overwhelmingly female—has risen strongly. (7) the median salary of $61,000 a year in 2012 was 55 percent greater, adjusted for inflation, than it was three decades earlier. (8) back then, more than a quarter of middle-income jobs were in manufacturing, a sector long dominated by men. (9) now, as of 2015, it is just 13 percent. (10) tabitha waugh is one success story; the daughter of a teacher's aide and a gas station manager, she now works as a registered nurse for $27 an hour.