Welfare-Enhancing Technological Change and the Growth of Obesity.

socioeconomic, and demographic characteristics. The data consist of both self-reported information on health, and information obtained by medical care providers from physical examination and laboratory analysis of blood and urine samples. Of the 33,994 total NHANES participants, 29,314 have available data on blood samples. We use information from the blood samples to assess the existence of specific micro-nutrient deficiencies. Standard medicine and pediatrics textbooks (cf, Bhattacharya and Currie, 2001; Braunwald et al., 2001) define serum normal values for these conditions, below which patients are seen as deficient. We focus in particular on four measures of nutritional status with clear and well-established links to diet: Vitamin A deficiency; Vitamin C deficiency; insufficient serum folate; and anemia. Vitamin A Deficiency is defined as having serum Vitamin A levels that fall below 1.05 umol/L. People with Vitamin A deficits can suffer problems with their vision, such as night blindness or ocular deterioration. Fruit and milk (which, in the US, is fortified with Vitamin A) represent its most important nutritional sources.