Not all, but many. At least in California.
Here is where I draw this conclusion from.
I make really good money, at least I think so, and my job is easy! Air conditioned office, flexible hours, it can be mentally taxing at times, but generally its pretty smooth sailing.
Constrast that with the people here in California picking lettuce, strawberries, and tomatoes. Day in and day out that work is physically demanding, boring as hell (which takes a huge mental toll) and they get paid about 10% of what I do!
Then look at the senior management of my company, some of these guys take in TENS OF MILLIONS per year, is their job that hard? Not at all. They are generally smart, assertive people that make consistently good (and profitable) decisions. They are highly educated in most cases, have a certain charisma and presence that lends themselves to leadership roles.
maybe I am the exception, but I'll admit it, I don't work even half as hard as someone who washes cars or picks produce for a living. If someone offered me a raise to take one of those jobs I'd decline in a heartbeat!