One of the guys at my conversation club was asking about the history of the hamburger so I looked it up and found this page.
According to it, McDonalds uses 7.5% of all the potatoes in the U.S. to make it's fries each year. That in 1992, 17 percent of all meal transactions were Hamburgers. And, that the average American eats 3 hamburgers a week.
I in turn asked him when Curry became popular in Japan since it's now as basic in Japan as say Spagetti in the states and he said that it was soldier food during the war. Japanese in general didn't used to eat lots of vegatables outside of rice and pickles and so covering the vegatables (potatoes and carrots) with curry was a way to get the soldiers to eat them.