Measuring and tracking obesity inequality in the United States: evidence from NHANES, 1971-2014.

BACKGROUND: Because people care about their weight relative to peers and society, obesity inequality plays a role in explaining obesity incidence and the impacts of being obese on subjective well-being. While the increase in obesity prevalence and mean body mass index (BMI) is well documented, the measurement of distributional changes and corresponding obesity inequality is yet to be fully explored. METHODS: The present study analyzed BMI data for adults aged 20 to 74 from the National Health and Nutritional Examination Survey (NHANES) I (1971-1974), II (1976-1980), III (1988-1994), and continuous NHANES (1999-2014). We applied tools developed to measure income inequality to analyze the inter-temporal variation in the BMI distribution among US adults. Using stochastic dominance tests, we construct partial orderings on cumulative BMI distributions during the study period. Shapley decompositions and inequality indices are employed to quantify the source and extent of temporal variation and decompose the inequality into within and between-group components considering age, gender, and race. RESULTS: The BMI distribution of each NHANES study first-order stochastically dominated the BMI distribution of the previous wave from 1971-1974 to 2003-2006, whereas more recent comparisons failed to reject the null hypothesis of non-dominance. The Shapley decomposition analysis revealed that horizontal shifts of BMI distributions accounted for a majority of the increase in obesity prevalence since 1988-1991. Especially in recent years when the rate of obesity growth has slowed down, the contribution of the redistribution component dropped significantly and even became negative between 2007-2010 and 2011-2014. The inequality indexes consistently show a worsening of obesity inequality from the mid-1970s to the mid-2000s regardless of population subgroups, and this disproportionate shift of the BMI distribution is unlikely to be a result of a changing ethnic composition of the US population. CONCLUSION: Our findings demonstrate that seemingly similar increases in obesity prevalence can be accompanied by very different patterns of distribution change. We find that the early phase of the obesity epidemic in the US was largely driven by increasing skewness, whereas more recent growth is a population-wide experience, regardless of demographic characteristics. Increasing morbid obesity certainly played an important role in the initial phase of the epidemic, but more recently the BMI distribution has largely horizontally shifted to the right.

State of the science and challenges of breeding landscape plants with ecological function.

Exotic plants dominate esthetically-managed landscapes, which cover 30-40 million hectares in the United States alone. Recent ecological studies have found that landscaping with exotic plant species can reduce biodiversity on multiple trophic levels. To support biodiversity in urbanized areas, the increased use of native landscaping plants has been advocated by conservation groups and US federal and state agencies. A major challenge to scaling up the use of native species in landscaping is providing ornamental plants that are both ecologically functional and economically viable. Depending on ecological and economic constraints, accelerated breeding approaches could be applied to ornamental trait development in native plants. This review examines the impact of landscaping choices on biodiversity, the current status of breeding and selection of native ornamental plants, and the interdisciplinary research needed to scale up landscaping plants that can support native biodiversity.

What do consumer surveys and experiments reveal and conceal about consumer preferences for genetically modified foods?

Assessing consumer perceptions and willingness to pay for genetically modified (GM) foods has been one of the most active areas of empirical research in agricultural economics. Researchers over the past 15 years have delivered well over 100 estimates of consumers' willingness to pay for GM foods using surveys and experimental methods. In this review, we explore a number of unresolved issues related to three questions that are critical when considering the sum of the individual contributions that constitute the evidence on consumer preferences for GM foods.

Rationing health protection: a proposal to exempt nuisance dust from US Clean Air Act regulations.

The US House of Representative has passed a bill called the "Farm Dust Regulation Prevention Act" (Dust Act) that would exempt most types of particulate matter (PM) in rural areas from the air quality controls of the US Clean Air Act. The Dust Act would markedly change the country's air quality standards. An examination of the proposed provisions shows that they would exempt non-combustion PM pollutants from mining, smelting, petroleum production, and power generation from existing air quality standards. Persons downwind from pollutants generated in rural areas could be exposed to concentrations of carcinogenic heavy metals, asbestos, and benzene known to adversely affect their health and ecological resources. Existing federal air quality standards based on science would be replaced by a flexible standard that rations health protection.