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Not raising the minimum wage with inflation will make your country fat

Via Greg Mankiw, here is a new working paper by David O. Meltzer and Zhuo Chen: “The Impact of Minimum Wage Rates on Body Weight in the United States“. The abstract:

Growing consumption of increasingly less expensive food, and especially “fast food”, has been cited as a potential cause of increasing rate of obesity in the United States over the past several decades. Because the real minimum wage in the United States has declined by as much as half over 1968-2007 and because minimum wage labor is a major contributor to the cost of food away from home we hypothesized that changes in the minimum wage would be associated with changes in bodyweight over this period. To examine this, we use data from the Behavioral Risk Factor Surveillance System from 1984-2006 to test whether variation in the real minimum wage was associated with changes in body mass index (BMI). We also examine whether this association varied by gender, education and income, and used quantile regression to test whether the association varied over the BMI distribution. We also estimate the fraction of the increase in BMI since 1970 attributable to minimum wage declines. We find that a $1 decrease in the real minimum wage was associated with a 0.06 increase in BMI. This relationship was significant across gender and income groups and largest among the highest percentiles of the BMI distribution. Real minimum wage decreases can explain 10% of the change in BMI since 1970. We conclude that the declining real minimum wage rates has contributed to the increasing rate of overweight and obesity in the United States. Studies to clarify the mechanism by which minimum wages may affect obesity might help determine appropriate policy responses.

Emphasis is mine.  There is an obvious candidate for the mechanism:

  1. Minimum wages, in real terms, have been falling in the USA over the last 40 years.
  2. Minimum-wage labour is a significant proportion of the cost of “food away from home” (often, but not just including, fast-food).
  3. Therefore the real cost of producing “food away from home” has fallen.
  4. Therefore the relative price of “food away from home” has fallen.
  5. Therefore people eat “food away from home” more frequently and “food at home” less frequently.
  6. Typical “food away from home” has, at the least, more calories than “food at home”.
  7. Therefore, holding the amount of exercise constant,  obesity rates increased.

Update: The magnitude of the effect for items 2) – 7) will probably be greater for fast-food versus regular restaurant food, because minimum-wage labour will almost certainly comprise a larger fraction of costs for a fast-food outlet than it will for a fancy restaurant.

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Fat = lower wages on average?

Via Steven Levitt, here’s an interesting paper by Roy Wada and Erdal Tekin:  “Body Composition and Wages”

This paper examines the effect of body composition on wages. We develop measures of body composition – body fat (BF) and fat-free mass (FFM) – using data on bioelectrical impedance analysis (BIA) that are available in the National Health and Nutrition Examination Survey III and estimate wage models for respondents in the National Longitudinal Survey of Youth 1979. Our results indicate that increased body fat is unambiguously associated with decreased wages for both males and females. This result is in contrast to the mixed and sometimes inconsistent results from the previous research using body mass index (BMI). We also find new evidence indicating that a higher level of fat-free body mass is consistently associated with increased hourly wages. We present further evidence that these results are not the artifacts of unobserved heterogeneity. Our findings are robust to numerous specification checks and to a large number of alternative BIA prediction equations from which the body composition measures are derived.

Our work addresses an important limitation of the current literature on the economics of obesity. Previous research relied on body weight or BMI for measuring obesity despite the growing agreement in the medical literature that they represent misleading measures of obesity because of their inability to distinguish between body fat and fat-free body mass. Body composition measures used in this paper represent significant improvements over the previously used measures because they allow for the effects of fat and fat free components of body composition to be separately identified. Our work also contributes to the growing literature on the role of non-cognitive characteristics on wage determination.

Looking very briefly through the paper, they don’t seem to be looking at what I would have thought an important factor:  relative obesity.  Wada and Tekin don’t seem to postulate a mechanism for how body fat leads to lower wages on average.  While I’m happy to accept that it may come about because of lower productivity, it also seems reasonable to ask if it’s also partially because of a selection bias by employers.  On that basis, looking at how much fat a person is carrying relative to their community average would seem to be important.

Update:  I’m obviously assuming both causality and direction of causality here, but my comment still holds.  A strong result on my suggested extra regressor would, to me, seem to provide evidence of that causality.