The cost of food has actually declined in the United States in the last century as a proportion of our salaries. GOOD magazine found that Americans spent 22 percent of their income on food in 1949 but only 10 percent in 2009. We also spend significantly less on food than people in other countries do, according to the USDA Economic Research Service .
Note, however, these data are from 2005 and account only for food eaten at home. The U.S. Department of Labor reports that in 2009 Americans spent 7 percent of their income on food eaten at home and another 5.4 percent on food eaten away from home (plus about 1 percent on alcohol). This information is based on surveys conducted by the Bureau of Labor Statistics (meaning it's based on self-reporting and interviews) and does not include what percentage of our income goes toward taxes (which would inflate the food expenditure percentages).
The fact that people in wealthier countries spend a smaller percentage of disposable income on food than people in poorer countries is unsurprising. In the 19th century, German statistician and director of the Bureau of Statistics in Prussia Ernst Engel came up with a theory, now known as Engel's law , which states that as income rises, food expenditures rise, but not as much as income. In 2006, Forbes found the same results among the various income levels of Americans.
We also aren't comparing apples to apples here. If an Indonesian made the same amount of money that I do and food costs in Indonesia were the same as they are here, these statistics might be more significant. According to Oxfam, Indonesians make between $1.40 and $1.75 a day. A kilo of rice costs less than 50 cents, which sounds like very little to us but devours an enormous percentage of the wages of an Indonesian. Here you can get a similar amount of rice for about $3, or twice what an Indonesian makes in a day.
It might be nice to know that in some ways Americans are better off than previous generations and some people in other countries, but we live within our own time and country and our own income brackets. And it can still feel painful handing over your dollars every week in the checkout line.