Mary A. Burke

Classroom Peer Effects and Student Achievement

We analyze the impact of classroom peers’ ability (measured by their individual fixed effects) on student achievement for all Florida public school students in grades 3–10 over a 6-year period. We control for both student and teacher fixed effects, thereby alleviating biases due to endogenous assignment of both peers and teachers. Under linear-in-means specifications, estimated peer effects are small to nonexistent, but we find some sizable and significant peer effects within nonlinear models. We also find that classroom peers, as compared with the broader group of grade-level peers at the same school, exert a greater influence on individual achievement gains.

From “Overweight” to “About Right”: Evidence of a Generational Shift in Body Weight Norms

In this article, we describe differences in the self‐perception of weight status in the United States between the two most recent National Health and Nutrition Examination Survey (NHANES) periods (1988–1994 and 1999–2004), and test the hypothesis that secular increases in adult mean BMI, adult obesity, and childhood obesity contributed to changes over time in weight perceptions. We find that the probability of self‐classifying as overweight is significantly lower on average in the more recent survey, for both women and men, controlling for objective weight status and other factors. Among women, the decline in the tendency to self‐classify as overweight is concentrated in the 17–35 age range, and is more pronounced among women with normal BMI than those with overweight BMI. Among men, the shift away from feeling overweight is roughly equal across age groups. Overweight men exhibit a sharper decline in feeling overweight than normal weight men. Despite the declines in feeling overweight between surveys, weight misperception did not increase significantly for men and decreased by a sizable margin among women. We interpret the findings as evidence of a generational shift in social norms related to body weight. As a result, people may be less likely to desire weight loss than previously, limiting the effectiveness of public health campaigns aimed at weight reduction. On the other hand, there may be health benefits associated with improved body image.

Social Dynamics of Obesity

In order to explain the substantial recent increases in obesity rates in the United States, we consider the effect of falling food prices in the context of a model involving endogenous body weight norms and an explicit, empirically grounded description of human metabolism. Unlike previous representative agent models of price-induced gains in average weight, our model, by including metabolic heterogeneity, is able to capture changes in additional features of the distribution, such as the dramatic growth in upper-quartile weights that are not readily inferred from the representative agent setting. We calibrate an analytical choice model to American women in the 30-to-60-year-old age bracket and compare the model’s equilibrium weight distributions to data from NHANES surveys spanning (intermittently) the period from 1976 through 2000. The model predicts increases in average weight and obesity rates with considerable accuracy and captures a considerable portion of the relative growth in upperquantile weights. The differential response to price declines across the distribution depends on the fact that human basal metabolism (or resting calorie expenditure) is increasing and yet concave in body weight, and therefore food price effects on weight tend to be larger for individuals who are heavier initially. The lagged adjustment of weight norms helps to explain recent observations that obesity rates have continued to rise since the mid 1990s, despite an apparent leveling off of price declines. The predicted increase in body weight aspirations agrees with an observed trend in self-reported desired weights, and it defies the conventional wisdom that thinness has been a growing obsession among American women in recent decades.

The emergence of local norms in networks

We develop an explanation of the emergence of local norms and the associated phenomenon of geographical variation in behavior. Individuals are assumed to interact locally with neighbors in an environment with a network externality. Although many patterns of behavior are possible, the dispersed interactive choices of agents are shown to select behavior that is locally uniform but globally diverse. The range of applications of the theory includes regional variation in the practice of medicine, technology choice, and corruption. The framework is also useful for further developing our understanding of important phenomena like lock-in, critical thresholds, and contagion.

The Strength of Social Interactions and Obesity among Women

In order to explain the differences in obesity rates among women in the United States by education, we model a social process in which body weight norms are determined endogenously in relation to the weight distribution of the peer group. The model features biologically grounded variation in metabolism, and enables us to describe a complete distribution of weights in equilibrium. We assume that individuals compare themselves to others with the same level of education, and that the importance of conforming to the group weight norm increases with education status. Consistent with observed body weights among women in the United States, the model predicts lower average weights and less dispersion of weight among more educated women.

An evolutionary model of debt

Abstract We study the emergence of institutions that facilitate lending within the context of a reputational model of debt. Taking an evolutionary perspective, we examine a game played between randomly matched players, and ask whether debt can be supported in the long run when lenders are given the option of joining an information-sharing coalition. Despite the fact that players are assumed to be unsophisticated, and follow simple adaptive rules, we observe steady states with widespread lending. The game also has steady states with no borrowing or lending, and these can persist in the long run. Using a mix of analytical and computational methods, we identify stable outcomes and provide an explanation for our results. The findings are shown to have broad implications for the study of institutional change and the feasibility of collective action through voluntary association.

Has Overweight Become the New Normal?: Evidence of a Generational Shift in Body Weight Norms

We test for differences across the two most recent NHANES survey periods (1988-1994 and 1999-2004) in self-perception of weight status. We find that the probability of self-classifying as overweight is significantly lower on average in the more recent survey, for both men and women, controlling for objective weight status and other factors. Among women, the decline in the tendency to self-classify as overweight is concentrated in the 17-35 age range, and, within this range, is more pronounced among women with normal BMI than among those with overweight BMI. Among men, the shift away from feeling overweight is roughly equal across age groups, except that the oldest group (56-74) exhibits no difference between surveys. In addition, overweight men exhibit a sharper decline in feeling overweight than normal-weight men. Despite the declines in feeling overweight between surveys, weight misperception did not increase significantly for men and decreased by a sizable margin among women. The shifts in self-classification are not explained by differences between surveys in body fatness or waist circumference, nor by shifting demographics. We interpret the findings as evidence of a generational shift in social norms related to body weight, and propose various mechanisms to explain such a shift, including: (1) higher average adult BMI and adult obesity rates in the later survey cohort, (2) higher childhood obesity rates in the later survey cohort, and (3) public education campaigns promoting healthy body image. The welfare implications of the observed trends in self-classification are mixed.

Evolving Societal Norms of Obesity: What Is the Appropriate Response?

The prevalence of obesity in the United States has increased substantially since the late 1970s—more than doubling among adults (20 years and older) and nearly tripling among youth (aged 2-19 years). According to data from the 2013-2014 National Health and Nutrition Examination Survey (NHANES),1 both the prevalence of adult obesity and the prevalence of youth obesity achieved all-time highs, 37.7% for adults and 17.2% for youth. Less well-known is that the perceptions of individuals about their own weight status have also changed in recent decades. Between the early 1990s and the early 2000s, the percentage of overweight (but not obese) individuals who described their weight as “about right” (rather than “overweight”) increased significantly, from 14% to 21% among women and from 41% to 46% among men. The percentage of obese individuals who felt about right also increased slightly, from 3.5% to 4% among women and from 11% to 12% among men, but these changes were not statistically significant.2 A related development in recent decades is the advent of the fat acceptance movement, which promotes social acceptance of a wide range of body sizes, includ-

You can be too thin (but not too tall): Social desirability bias in self-reports of weight and height

HighlightsReasons for self‐reporting errors in weight and height are tested using NHANES data.Self‐reports of weight offer robust evidence of social desirability bias.However, lack of awareness of weight may contribute to self‐reporting biases.Results have important implications for survey design and for clinical practice. ABSTRACT Previous studies of survey data from the U.S. and other countries find that women tend to understate their body weight on average, while both men and women overstate their height on average. Social norms have been posited as one potential explanation for misreporting of weight and height, but lack of awareness of body weight has been suggested as an alternative explanation, and the evidence presented to date is inconclusive. This paper is the first to offer a theoretical model of self‐reporting behavior for weight and height, in which individuals face a tradeoff between reporting an accurate weight (or height) and reporting a socially desirable weight (or height). The model generates testable implications that help us to determine whether self‐reporting errors arise because of social desirability bias or instead reflect lack of awareness of body weight and/or other factors. Using data from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2010, we find that self‐reports of weight offer robust evidence of social desirability bias. However, lack of awareness of weight may also contribute to self‐reporting biases, and this factor appears to be more important within some demographic groups than others. Among both women and men, self‐reports of height exhibit significant social desirability bias only among those of below‐average height, and very few individuals underreport their height. Implied self‐reports of BMI exhibit gender‐specific patterns similar to those observed for self‐reporting of weight, and the inferred social norms for BMI (20.8 for women and 24.8 for men) are within the “normal” range established by public health institutions. Determining why individuals misreport their weight has important implications for survey design as well as for clinical practice. For example, our findings suggest that health care providers might take additional steps to increase self‐awareness of body weight. The framework also helps to explain previous findings that the degree of self‐reporting bias in weight is stronger in telephone surveys than it is in in‐person surveys.

Explaining gender-specific racial differences in obesity using biased self-reports of food intake

Policymakers have an interest in identifying the differences in behavior patterns - namely, habitual caloric intake and physical activity levels - that contribute to demographic variation in body mass index (BMI) and obesity risk. While disparities in mean BMI and obesity rates between whites (non-Hispanic) and African-Americans (non-Hispanic) are well-documented, the behavioral differences that underlie these gaps have not been carefully identified. Moreover, the female-specificity of the black-white obesity gap has received relatively little attention. In the National Health and Nutrition Examination Surveys (NHANES) data, we initially observe a very weak relationship between self-reported measures of caloric intake and physical activity and either BMI or obesity risk, and these behaviors appear to explain only a small fraction of the black-white BMI gap (or obesity gap) among women. These unadjusted estimates echo previous findings from large survey datasets such as the NHANES. Using an innovative method to mitigate the widely recognized problem of measurement error in self-reported behaviors - proxying for measurement errors using the ratio of reported caloric intake to estimated true caloric needs - we obtain much stronger relationships between behaviors and BMI (or obesity risk). Behaviors can in fact account for a significant share of the BMI gap (and the obesity gap) between black women and white women and are consistent with the presence of much smaller gaps between black men and white men. The analysis also shows that the effects smoking has on BMI and obesity risk are small-to-negligible when measurement error is properly controlled.