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Socioeconomic Determinants of Body Mass Index of Adult Chinese in the 1990s. Zhehui Luo, Ph.D. MS Department of Epidemiology Michigan State University. Outline. Simple Model Data and Econometric Issues Trends and Descriptives Results of Reduced Form Demand Results of Dynamic Demand
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Socioeconomic Determinants of Body Mass Index of Adult Chinese in the 1990s Zhehui Luo, Ph.D. MS Department of Epidemiology Michigan State University
Outline • Simple Model • Data and Econometric Issues • Trends and Descriptives • Results of Reduced Form Demand • Results of Dynamic Demand • Results of Production Function
The Model s. t.
The Model • If total time available for leisure and work is not affected by health status • Labor is the same as the effective labor in Grossman’s sense • Equilibrium condition is:
The Data • Chinese Health and Nutrition Survey (CHNS) 1989, 1991, 1993 and 1997 • Carolina Population Center at the University of North Carolina, Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medicine • Sampling: multistage, random cluster process
Adults aged 20 and above Excluding pregnant women Sample size: 1989: 4550 persons, 2736 households 1991: 7356 persons, 3402 HH 1993: 6926 persons, 3164 HH 1997: 7580 persons, 3512 HH The Data
The Data • BMI: Weight (kg)/ height (m2)
The Data • Calorie, fat, protein intakes and percent of Calories from fat, protein and carbohydrates • The 1991 China Food Composition Table • 1 gram fat = 9 Kcal energy 1 gram protein = 4 Kcal energy 1 gram carbohydrates=4 Kcal energy
Trends in Food Availability Source: FAO 2002 Food Balance Sheet for China
Trends in overweight and obesity % Men and Women overweight (BMI 25) % Men and Women obese (BMI 30)
% Men overweight by age groups % Women overweight by age groups Trends in overweight
% Men overweight by rural-urban residence % Women overweight by rural-urban residence Trends in overweight
% Men overweight by education levels % Women overweight by education levels Trends in overweight
BMI Distribution: Men Russel Davidson and Jean-Yves Duclos (2000), performed with DAD 4.3
BMI Distribution: Women Russel Davidson and Jean-Yves Duclos (2000), performed with DAD 4.3
Estimating Equation The linear representation: Baltagi and Wu (1999)
Estimating Equation • Econometric Issues • Measurement Errors • Functional form: nonlinearity of effects • Age, cohort and period effects
Age, Period and Cohort Analysis • To identify: • Origin-related process – cohort effect dominant • Aging process • Instantaneous process – function of time • Linear dependency: • Deaton (1997), Holford (1983)
Age, Period and Cohort Analysis • Spacing of the data determines the number of extra constraints (n) needed • CHNS 1989, 1991, 1993, 1997: n=2 • If arbitrarily impose two constraints:
Age, Period and Cohort Analysis • Meaningful constraints: Source: State Statistical Bureau (1992): 1990 Population Census of China.
Age, Period and Cohort Analysis • Results from age dummies, five-year cohort dummies and year dummies:
Reduced Form Demand (I) • Results from the basic model: • Education effect on female BMI inversely U-shaped • % Calories from fat and protein increase with education • Male BMI increases with productive assets, female inversely U-shaped • % Calories from fat and protein increase with assets, except for urban men – U-shaped
Reduced Form Demand (II) • Results from the augmented model: • Prices significant without controlling community dummies in BMI regressions • Negative price elasticity of rice, eggs for calories, fat and protein; positive price elasticity of pork • Better water source – fat, protein intakes and male BMI: positive • More excreta – calories and protein: negative
Dynamic BMI Demand • Estimating Equation: • Instruments: previous years HH resources, community characteristics • Results: • In short terms lagged BMI is good summary measure of health status • Age effect for women still strong, aging factor
BMI Production Function • Estimating equation: • Instruments: previous years HH resources, community characteristics • Results: • In a short period, BMI – a random walk process • Heavy physical activities negative in OLS and positive in IV • Food intakes not significant
Limitations and Future research • Measurement: productive assets, fat intake • Uncertainty • Attrition • Health and Labor Market Participation • Intra-household allocation and Health