Marriage

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Marriage makes you fat

September 24, 2009 in My Papers | 1 comment

Researches at UNC found that marriage may make you happy and healthy but fat as well.  If you’ve been a loyal reader of the Healthcare Economist, however, you knew that already.

Jason Shafrin’s research on marriage and weight gain already showed that marriage leads to increased weight gain.  In fact, the research demonstrated that one reason marriage causes weight gain is that individual who get married experience a decreased incentive to maintain their weight in order to attract a significant other (read the paper).  These findings were also presented at the Western Economic Association International (WEAI) conference in Vancouver this June.  Below is an abstract of the paper:

Married individuals weigh more on average than non-married individuals. We suggest that exiting the dating market decreases ones incentive to maintain their appearance and leads to an increase in body weight. We hypothesize that it is most difficult for individuals to exit a traditional marriage, and easiest for individuals to exit if the couple is cohabitating but not legally married. Using a 14-year panel data set, we test whether or not the ease of exiting a domestic relationship affects weight gain. For men, we find that the type of domestic relationship has little impact on weight gain. For women, however, marriage leads to a 2.4 kg weight gain compared to cohabitating.

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Are all the good men married?

December 9, 2008 in Labor Economics | No comments

Does marriage cause men’s wages to rise?  This is the question addressed by UCSD professor Kate Antonovics and Robert Town in their 2004 paper in AER cleverly titled “Are all the good men married?”

It has been shown that married men earn more money than non-married men with similar characteristics.  Why is this?  A few explanations are:

  1. Married men are more productive since they specialize in non-household production,
  2. Employers could discriminate in favor of married men, or
  3. the unobservable characteristics that make men more productive in the labor market also make them more attractive in the marriage market.
A simple way to figure out the marriage wage premium is to run an OLS regression.
  • wij = βMij + γXij + μij + fj + uij   (1).
  • M: married, X: other variables, μ: individual fixed effect, f: family fixed effect, u: error term 
  • For OLS, the residual is equal to μij + fj + uij   (1).

Using OLS, the authors find that married men earn a 19% wage premium over non married men.  However, this specification does not solve the selection problem.  If it is true that unobservable factors affect wages and marriage eligibility, then the marriage dummy variable will be correlated with the residual and β may be biased upwards.  

How do the authors solve the endogeneity problem?  They use data from the Socioeconomic Survey of Twins.  For a pair of monozygotic twins, we can rewrite equation (1) as follows:

  • w1j= βM1j + γX1j + μ1j + fj + u1j  (2)
  • w2j = βM2j + γX2j + μ2j + fj + u2j  (3)

Since twins are in the same family, we know that fj in both equation is the same.  Further, we assume that the genetically determined, individual specific earnings endowment is the same across twins (i.e., μ1j = μ2j). Thus we can difference out the two equations so that we are left with:

  • w1j – w2j = β(M1j – M2j) + γ (X1j – X2j) + (u1j – u2j)  (4)
Using this specification on the twin data, the authors find that marriage confers a 26% wage increase.  Because of the similarity between the OLS and twin data, the authors claim that “men are not selecting into marriage based on unobserved heterogeneity in earnings capacity.”

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Marriage and weight gain

November 17, 2008 in Obesity | No comments

Do people gain weight after marriage?  A paper by Jeffrey and Rick (2002) says yes.  Using data collected from 2528 workers over a 2 year period, the authors estimated the effect of marriage and divorce on weight gain.  They found the following:

Getting married increases BMI by 0.70 for men and 0.96 for women.  For the average American male and female, this translates into a 4.8 pound increase for men and a 5.6 pound increase for women.  

Getting divorced actually decreases BMI.  The coefficients estimated were -0.27 for men and -0.63 for women; this translates into weight losses of 1.8 pounds for men and 3.7 pounds for women.  

The authors also found that “spouses tend to become more similar in body weight over time, indicating that environmental influences are an important cause of spouse weight similarity.”

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Evidence that Women are the stronger sex: Mortality after the death of a spouse

September 30, 2008 in Academic Articles | Permalink

A few papers have found that mortality rises after the death of the spouse.  Some researchers have inferred that this is due to a causal effect of this emotionally traumatic event.  Further, married individuals generally live longer, so the loss of this “marriage protection” could be the cause of increased mortality.  On the other hand, it could be the case that spouses “select” to partner with each other and engage in similar eating and exercise habits and thus have similar mortality.  Further, spouses often partner on the basis of income-generating capacity and education which are also correlated with mortality.  So does the death of a spouse cause an increase in mortality or is this just a case of marriage selection?

This question is what a paper by Espinosa and Evens (JHE 2008) tries to uncover.  This authors look at informative deaths–deaths due to health an individual’s health condition–compared with uninformative deaths (e.g., motor vehicle accident, homicide).  The authors find that men have a significant increase in mortality after the death of their spouse even when the death is “uninformative.”  This authors conclude that for males, this bereavement effect of losing a wife is causing increased mortality.

For women, “The bereavement effect for surviving wives when their husband dies of an uninformative cause is small but with a large standard error, making it statistically indistinguishable from the effect for informative causes.” Thus, there seems that the death of a woman’s husband does not cause increased mortality.

Here is some scientific evidence that women are the stronger sex.

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Marital Status and Body Weight Changes

March 10, 2008 in Obesity | 3 comments

Why do people want to lose weight? While this seems like an obvious question, it does merit answering. There are two major reasons: health concerns and appearance. Being obese increases the risk of suffering from many diseases (e.g.: diabetes). On the appearance side, individuals may experience social pressure to lose (or possibly gain) weight. Further, individuals may want to maintain a healthy body appearance to attract a mate.

Jeffery Sobal is an expert in obesity studies. According to his 2003 study, activities which directly affect weight are caloric intake, physical activity and smoking.

One of the more interesting questions is how an individual’s marriage status affects obesity. It is generally found that–even controlling for age and other covariates–married individuals are more likely to be overweight than non-married individuals. Why is this the case. Sobal cites some studies which attempt to explain this.

After citing all this evidence, Sobal and co-authors state 4 hyptotheses to test:

  1. Marital trajectories that are stable are related to stable body weights,
  2. marital trajectories entering marriage are related to weight gain,
  3. marital trajectories dissolving marriage are related to weight loss,
  4. marital trajectories involving the death of a spouse are related to weight loss.

Sobal uses data from from the National Health and Nutritional Examination Survey (NHANES I). A 10 year follow up survey of the participants is collected in the National Health and Nutrition Epidemiological Followup Survey (NHEFS). The authors use an OLS specification with a lagged dependent variable (i.e., lagged BMI) in order to estimate the impact of marital status on weight. Sobal, Rauschenbach and Frongillo conclude the following:

  1. Stable marital trajectories were not associated with significant weight changes, except for weight loss among men who remained separated/divorced.
  2. Marital trajectories involving entry into marriage were associated with weight gain among women, but not among men.
  3. Marital trajectories involving dissolving marriages were associated with weight loss among men, but not women.
  4. Marital trajectories involving death of a spouse were associated with weight loss among men, but not women.
  5. Marital and other demographic characteristics were better predictors of weight loss than weight gain.

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Marriage and Obesity

November 28, 2007 in Obesity | Permalink

Are married people more likely to be obese than single individuals? More to the point, does being married cause obesity? Married individuals are generally older than never-married individuals and since age is correlated with obesity, there could be a spurious relationship between marriage and obesity.

One may think that married individuals are not on the “single’s market” and thus may not have a strong incentive to maintain an athletic physical appearance to attract mates. As stated in Sobal (1984), “We may hypothesize that as a marital relationship becomes solidified the partners may feel less need to maintain external appearances important in attracting a mate.” On the other hand, a paper by Rand, Kuldau and Robbins (JAMA 1982) found that individuals who had jejunoileal bypass surgery to decrease obesity had improved marriage relationships. Thus, those who value their marriage may wish to avoid being overweight to make the marriage experience more pleasurable.

If healthier individuals can more easily attract a mate, than it would be the case that married individuals will be less overweight than single individuals. Averett and Korenman (Int J Obesity 1999) found that obesity is associated with a lower probability of marriage. Gortmaker et al. (NEJM 1993) use the NLSY to conclude that individuals who where overweight in their adolescent years are 20% less likely to be married seven years later than a healthy-weighted individual. Cawley, Joyner and Sobal (Rationality and Society 2006) confirm that for adolescents “dating is less likely among heavier girls and boys and among shorter girls and boys.”

Sobal, Rauschenbach and Frongillo (Soc Sci Med 1992) categorizes the relationship between obesity as marriage through two distinct mechanisms: “marital selection” and “marital causation.” Non-overweight people are more likely to attract a mate, and thus “select” into marriage. However, if marriage “causes” weight gain–due to a more sedentary lifestyle, lower mate attraction incentive, childbirth, etc.–than a researcher may find that married individuals are more overweight on average.

The best way to control for these two conflicting effects is to use a panel data set. Cawley (JHR 2004) employs the 1979 NLSY, using lagged BMI as an instrument for current BMI and individual fixed effects to control for time-invariant individual characteristics. Other studies have used sibling weight (Avarett and Kroenman (JHR 1996), or spousal weight as an instrument for current BMI. Using data from the National Survey of Personal Health practices and consequences, the Sobal, Rauschenbach and Frongillo paper finds that “it appears that there is a relationship between fatness and marital status for men, with married men fatter and more obese.”

Nevertheless, more research is needed to refine the exact manner in which marriage affects obesity.

  • Averett S and Korenman S. 1996. “The Economic Reality of the Beauty Myth.” J Human Resources. 31(2): 304-330.
  • Averett S and Korenman S. 1999. “Black-white differences in social and economic consequences of obesity.” International Journal of Obesity. vol 23, pp. 166-173.
  • Cawley J. 2004. “The Impact of Obesity on Wages” J Human Resources. 39(2): 451-474.
  • Cawley J, Koyner K, Sobal J. 2006. ”Size Matters: The influence of adolescents’ weight and height on dating and sex.” Rationality and Society. Vol. 18, No. 1, 67-94.
  • Gortmaker SL, Must A, Perrin JM, Sobol AM, Dietz WH. 1993. “Social and Economic Consequences of Overweight in Adolescence and Young Adulthood.” NEJM. 329(14): 1008-1012.
  • Rand CS, Kuldau JM, Robbins L. 1982. “Surgery for Obesity and Marriage Quality.” 247(10): 1419-1422.
  • Sobal J. 1984. “Marriage, Obesity and Dieting.” Marriage and Family Review. 7:115-139.
  • Sobal J, Rauscehnbach BS, Frongillo EA. 1992. “Marital Status, Fatness and Obesity.” Social Science and Medicine. 35(7): 915-923.

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