Abstract
Extending Small and McDermott’s ‘conditional perspective’, Blalock’s minority competition theory is used to explain how the relationship between African Americans and the number of supermarkets in a zip code depends on the city in which it resides. The 2010 American Community Survey and ZIP Business pattern data are examined with hierarchical general linear models to explore whether the previously observed negative relationship between the percentage of African Americans and the number of supermarkets in a zip code depends on the percentage of African Americans in the city. The results show that the relationship between the percentage of African Americans and the number of supermarkets depends on the percentage of African Americans in the city in the U-shaped pattern predicted by minority competition theory. Applications of minority competition to other theories of the unequal distribution of resources in cities are discussed.
Generated Summary
This research article investigates the relationship between the racial composition of a city and the availability of supermarkets in its zip codes, specifically focusing on the role of African Americans as a predictor in “food deserts.” Employing a quantitative approach, the study extends Small and McDermott’s “conditional perspective” by examining how the association between the percentage of African Americans and the number of supermarkets in a zip code is contingent upon the city’s racial dynamics. The methodology involves the application of Hierarchical General Linear Modeling to the 2010 American Community Survey and ZIP Business Pattern data. The core of the analysis centers on testing the hypothesis that minority competition theory, as proposed by Blalock, can explain how city characteristics, particularly the percentage of African Americans, moderate the relationship between the percentage of African Americans and the number of supermarkets within a zip code. The scope of the study is limited to the examination of supermarket availability and does not delve into other aspects of food access or the complexities of food environments beyond the presence of supermarkets. Furthermore, the research acknowledges the limitations of solely examining the impact of demographic factors without fully exploring the broader causes of the relationship between demographics and supermarket locations, particularly the non-economic negative relationship between African Americans and supermarkets.
Key Findings & Statistics
- The study uses data from the 2010 ZIP business patterns to determine the number of supermarkets in each zip code.
- Table 1 provides summary statistics for the variables used, including mean percentages and standard deviations for variables like supermarkets, population density, percentage of African Americans, poverty, household income, and unemployment. The number of supermarkets had a mean of 1.25 and a standard deviation of 1.69. The percentage of African Americans had a mean of 0.67 and a standard deviation of 0.53. The percentage in poverty had a mean of 1.03 and a standard deviation of 0.34. The study uses logged variables, which are more interpretable but the model fit takes precedence.
- Table 2 presents the logged odds from models with only zip code (level 1) predictors. The main variable of interest, the percent of African Americans in a zip code, is statistically significant and negatively related to the number of supermarkets when controlling for percent in poverty (Model 1). However, when controlling for mean household income percent African Americans is not significant.
- Table 3 presents the logged odds from the multilevel Poisson model predicting the number of supermarkets in a zip code. This table looks at the predictors of the random intercept, city population density, unemployment, household income, and poverty, and shows how these variables interact. The main findings of the analysis indicate the direction and significance of city-level variables in determining supermarket placement.
- For every 10% increase in the percent in poverty in a zip code, there is a 15% increase (e^0.141) in the number of supermarkets (Table 2).
- The relationship between poverty and supermarkets is not robust: using grocery stores with over 50 employees instead of over 20 leads to a negative percent poverty slope (Table 2).
- Figure 1 demonstrates the non-linear moderation of the percentage of African Americans in the city on the relationship between the percentage of African Americans and the number of supermarkets in a zip code.
- At very low percentages of African Americans in a city, the negative slope is small. The negative slope is largest at medium levels of percent African American in the city. After 17% African American in the city (the inflection point), the negative slope begins to decrease slowly. Finally after around 33% African Americans in the city the slope again becomes increasingly negative; however this last point is less meaningful since less than 6% of MSAs have a percentage of African Americans over 33% (and less than 2.5% have over 40%).
Other Important Findings
- The research confirms a negative relationship between the percentage of African Americans and the number of supermarkets in a zip code.
- The study suggests that the relationship between African Americans and the number of supermarkets depends on the percentage of African Americans in the city, in a U-shaped pattern predicted by minority competition theory.
- The findings indicate that in areas with limited access to supermarkets, residents tend to have worse health outcomes, including higher rates of obesity, cardiovascular disease, and diabetes.
- The research suggests that supermarkets are more likely to avoid predominantly African American zip codes in more affluent and densely populated cities.
- The study notes that the West region has more supermarkets per zip code compared to other regions.
Limitations Noted in the Document
- The study’s primary limitation is the lack of measures of motivations to discriminate. The research acknowledges the challenge in measuring the specific forms of discrimination that push resources away from minorities.
- The study’s focus on supermarket locations overlooks broader causes of the relationship between demographics and supermarket locations, particularly the non-economic negative relationship between African Americans and supermarkets.
- The research does not fully explore the economic indicators as causes and effects of motivations to discriminate.
- The study is vulnerable to ‘edge effects’ due to the reliance on zip codes and a lack of precise measures of geographic proximity to supermarkets.
- The study’s generalizability is limited by the use of a single measure of stores with over 20 employees.
Conclusion
The study’s findings support the application of minority competition theory in understanding the unequal distribution of resources, specifically supermarkets, in urban settings. The research demonstrates a complex relationship between the percentage of African Americans in a city and the number of supermarkets in a zip code, showing that the relationship is moderated by the city-wide racial composition. The research indicates that the negative relationship between the percentage of African Americans and the number of supermarkets is contingent upon the city’s racial dynamics, mirroring the patterns suggested by minority competition theory. The study emphasizes that future research should focus on specific mechanisms of discrimination and the role of perceived threat, rather than solely on the economic aspects. This study contributes to the literature on “food deserts” and the broader understanding of how racial dynamics influence access to essential resources within communities. The minority competition theory framework offers a valuable lens for understanding how city characteristics, especially racial composition, shape resource distribution. The study’s results emphasize that the relationship between the percentage of African Americans and the number of supermarkets varies depending on the racial composition of the city, revealing a complex interaction. The research also highlights the need for a better understanding of the complex interplay between economic factors and racial dynamics in shaping urban inequality. This study provides insights that contribute to the understanding of urban resource distribution, suggesting that minority competition theory is useful in explaining how city dynamics moderate the location of organizations away from African Americans.