This paper reviews studies of the validity of commercially available business (CAB) data on food establishments (“the foodscape”), offering a meta-analysis of characteristics associated with CAB quality and a case study evaluating the performance of commonly-used validity indicators describing the foodscape. Existing validation studies report a broad range in CAB data quality, although most studies conclude that CAB quality is “moderate” to “substantial”. We conclude that current studies may underestimate the quality of CAB data. We recommend that future validation studies use density-adjusted and exposure measures to offer a more meaningful characterization of the relationship of data error with spatial exposure.

The firm is a fundamental economic unit of contemporary human societies. Studies on the general quantitative and statistical character of firms have produced mixed results regarding their lifespans and mortality. We examine a comprehensive database of more than 25 000 publicly traded North American companies, from 1950 to 2009, to derive the statistics of firm lifespans. Based on detailed survival analysis, we show that the mortality of publicly traded companies manifests an approximately constant hazard rate over long periods of observation. This regularity indicates that mortality rates are independent of a company's age. We show that the typical half-life of a publicly traded company is about a decade, regardless of business sector. Our results shed new light on the dynamics of births and deaths of publicly traded companies and identify some of the necessary ingredients of a general theory of firms.

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OBJECTIVES: To evaluate the association of the 2009 changes to the US Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) food package and childhood obesity trends. We hypothesized that the food package change reduced obesity among children participating in WIC, a population that has been especially vulnerable to the childhood obesity epidemic. METHODS: We used an interrupted time-series design with repeated cross-sectional measurements of state-specific obesity prevalence among WIC-participating 2-to 4-year-old children from 2000 to 2014. We used multilevel linear regression models to estimate the trend in obesity prevalence for states before the WIC package revision and to test whether the trend in obesity prevalence changed after the 2009 WIC package revision, adjusting for changes in demographics. In a secondary analysis, we adjusted for changes in macrosomia and high prepregnancy BMI. RESULTS: Before the 2009 WIC food package change, the prevalence of obesity across states among 2-to 4-year-old WIC participants was increasing by 0.23 percentage points annually (95% confidence interval: 0.17 to 0.29; P , .001). After 2009, the trend was reversed (20.34 percentage points per year; 95% confidence interval: 20.42 to 20.25; P , .001). Changes in sociodemographic and other obesity risk factors did not account for this change in the trend in obesity prevalence. CONCLUSIONS: The 2009 WIC food package change may have helped to reverse the rapid increase in obesity prevalence among WIC participants observed before the food package change. WHAT'S KNOWN ON THIS SUBJECT: Changes to the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) in 2009 decreased intake of foods and beverages associated with excess weight gain. Surveillance data suggest obesity prevalence among WIC-participating children declined from 2010 to 2014. WHAT THIS STUDY ADDS: We quantify the association of the WIC package change and childhood obesity using a quasi-experimental study design and accounting for state-level differences, race and/or ethnicity, poverty trends, and trends in macrosomia and high prepregnancy BMI among WIC participants.