Just one data-entry point (and it's from Eastern Europe, not the States): my brother picked up trucking in his mid-30s, that is 5-6 years ago. Until then he had been a farmer, but as the agricultural subsidies in my country can't rival with those given to French farmers (for example) there was no way for him to earn his living just by raising cows (even though he loved the farming work). Until this trucking job he had never been out of the country, in the meantime he has seen almost all of Europe up to Western Turkey. It's not a job for everybody, though: a month or so ago he was robbed of 240 liters of diesel fuel while he was in his sleep-pause somewhere in Bulgaria, he had just been waiting for 20 hours a short time before that at the Turkish-Bulgarian custom point, and he's usually gone 2 or even 3 weeks at a time.