Using New Measures of Fatness to Improve Estimates of Early
Retirement and Entry onto the OASI Rolls Richard V. Burkhauser John
C. Cawley
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Research Question Our research question: Is there a causal
relationship between fatness and taking Old-Age benefits at age 62?
Fatness is a risk factor for morbidity and mortality in the medical
literature Innovations: Utilize alternative measures of fatness to
capture health. Test for causal link using method of instrumental
variables.
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Discrete when health is continuous Error-ridden since
individuals scales are different Endogenous to retirement decision.
Bond, Steinbricker and Waidmann (2006) Problems with Subjective
Measures of Health
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Body Mass Index (BMI) BMI = kg/m 2 is most common measure of
fatness in social science research NIH, WHO use BMI to define
obesity (BMI>=30) Advantage: weight and height found in many
social science datasets, easy to calculate Disadvantage: BMI does
not distinguish between fat and muscle Overestimates fatness among
the muscular (U.S. DHHS, 2001; Prentice and Jebb, 2001)
Underestimates fatness among those with small frames
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Accurate Measures of Obesity Must Distinguish Body Composition
Fatness (not muscle/bone/blood) causes morbidity, mortality
Previous studies that define obesity using body mass index (BMI)
likely misstate correlation between fatness and economic outcomes
Better measure of fatness: Percent Body Fat (PBF) Obesity defined
as PBF>25 for men, PBF>30 for women (NIH, 2006)
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BMI Poor Measure of Fatness BMI alone accounts for just 25% of
between- individual differences in percent body fat (Gallagher et
al., 1996) False negatives: BMI correctly identifies only 44.3% of
obese men and 55.4% of obese women (judged by measurement of actual
body fat); Smalley et al (1990) False positives: 9.9% of non-obese
men and 1.8% of non-obese women. Smalley et al. (1990).