Because most previous demand studies have ignored these structural shifts, the effects of income on food demand have been overestimated. Because structural shifts are strongly correlated with increasing GNP per capita, it is difficult to separate the two effects empirically in time-series estimations. Unfortunately, methodologies for measuring the effects of structural shifts are not as well developed as those for measuring income and price effects. People are exposed to a variety of dietary patterns from foreign cultures. Urban lifestyles place a premium on foods that require less time to prepare.
Transaction costs are lower.
Urban occupations are more sedentary than rural ones, requiring fewer calories to maintain body weight. While changes in food demand patterns that cannot be attributed to increases in household incomes and changes in food prices may first be noticed in urban areas, as structural transformation proceeds to a more advanced level, these same shifts in food demand patterns eventually will occur in rural areas as well. At some point, market availability and lifestyles in urban and rural areas become virtually indistinguishable. Taiwan Household Expenditure Surveys Average diets may change dramatically in countries experiencing rapid economic growth and structural transformation. Consumers are substituting foods such as meat, fish, and fruit for staple foods such as rice, so that they now obtain a substantial share of their calories from constable foods.