The above graph illustrates how the marginal share for a food category varies by country based on the level of affluence. With low-income countries, a greater portion of an additional unit of food expenditures is allocated to cereals and fruits/vegetables, which include staples such as corn meal and rice. As countries become more affluent, the portion of additional food expenditures allocated to cereals and fruits/vegetables decreases, and a greater portion is allocated to “other” food expenditures, which includes restaurant expenditures and high-end purchases, and beverages/tobacco. ...
Conclusion
... Low-value staples, such as cereals, account for a larger share of the food budget in poorer countries, while high-value food items are a larger share of the food budget in richer countries. Low-income countries are also more responsive to changes in income and food prices and, therefore, make larger adjustments to their food consumption patterns when incomes and prices change. However, our study illustrates that adjustments to price and income changes are not made uniformly across all food categories. Staple food consumption changes the least, while consumption of higher-value food items changes the most. ...
source: usda [pdf]