Here's the way I figure it:
My wife's grandfather was a service worker in an oil company town. He didn't work on the oil rigs, he worked in town. He was at the bottom levels of the company pay scales, and he made less than most people in the field. On his salary he could afford to buy a house, a car, decent food and clothing for his family, he had a health plan, his children went to school, he could afford to take his wife out to dinner in good restaurants a few times a year, he could take his family to the movies once a week, and he could take his family on week long vacations to big cities. His pension when he retired was comfortable.
Compare his standard of living to a cane field worker of the present day, in a country like Brazil. Brazil is actually one of the better places. They don't have so many slaves there as they do in some places.
This is where you live, your house has no running water:
http://www.everychild.org.uk/inaction.php?pageId=62There are several reasons for this vast discrepancy in living standards. Some of them have to do with politics, the wealthy and powerful stealing from the poor, but to a much greater extent it is the difference between easy oil and ethanol from sugar cane. Sugar cane requires lots of labor for every gallon of ethanol made. The oil fields my wife's grandfather's company exploited were much richer. You drilled a hole a few hundred feet, and vast energy poured out of it.