while i was working for this xyz CDL marketing company, i did not come across any stats, but i saw fathers passing down the biz to their sons, and/or family members working all together to run their own trucking biz each playing various roles and running it quite efficiently. Since they do not have college degrees they are locked in and thus do successfully make a career of it, additionally some of them don't drink and have good driving records.
Also the sikh community inherently feels persecuted wherever they go due to their rigid beliefs, unfortunately this is also true in their homeland-India, but which in turn makes them help each other out even more, their community is well-organized and close-knit. There truly was a constant in-flux of new younger drivers who had plans of a long career.
Also, climate change/global warming was also another albatross around their necks...farming and produce are significantly affected each year due to floods an/or droughts