John M. Parman

Single-Strand Stacking Free Energy from DNA Beacon Kinetics

DNA beacons are short single-stranded chains which can form closed hairpin shapes through complementary base pairing at their ends. Contrary to the common polymer theory assumption that only their loop length matters, experiments show that their closing kinetics depend on the loop composition. We have modeled the closing kinetics and in so doing have obtained stacking enthalpies and entropies for single-stranded nucleic acids. The resulting change of persistence length with temperature effects the dynamics. With a Monte Carlo study, we answer another polymer question of how the closing time scales with chain length, finding tau approximately N(2.44+/-0.02). There is a significant crossover for shorter chains, bringing the effective exponent into good agreement with experiment.

The National Rise in Residential Segregation

This paper introduces a new measure of residential segregation based on individual-level data. We exploit complete census manuscript files to derive a measure of segregation based upon the racial similarity of next-door neighbors. Our measure allows us to analyze segregation consistently and comprehensively for all areas in the United States and allows for a richer view of the variation in segregation across time and space. We show that the fineness of our measure reveals aspects of racial sorting that cannot be captured by traditional segregation indices. Our measure can distinguish between the effects of increasing racial homogeneity of a location and the tendency to segregate within a location given a particular racial composition. Analysis of neighbor-based segregation over time establishes several new facts about segregation. First, segregation doubled nationally from 1880 to 1940. Second, contrary to previous estimates, we find that urban areas in the South were the most segregated in the country and remained so over time. Third, the dramatic increase in segregation in the twentieth century was not driven by urbanization, black migratory patterns, or white flight to suburban areas, but rather resulted from a national increase in racial sorting at the household level. The likelihood that an African American household had a non-African American neighbor declined by more than 15 percentage points (more than a 25% decrease) through the mid-twentieth century. In all areas of the United States -- North and South, urban and rural -- racial segregation increased dramatically.

The mortality consequences of distinctively black names

Race-specific given names have been linked to a range of negative outcomes in contemporary studies, but little is known about their long-term consequences. Building on recent research which documents the existence of a national naming pattern for African American males in the late nineteenth and early twentieth centuries (Cook, Logan and Parman, 2014), we analyze long-term consequences of distinctively racialized names. Using over 3 million death certificates from Alabama, Illinois, Missouri and North Carolina from 1802 to 1970, we find a robust within-race mortality difference for African American men who had distinctively black names. Having an African American name added more than 1 year of life relative to other African American males. The result is robust to controlling for the age pattern of mortality over time and environmental factors which could drive the mortality relationship. The result is not consistently present for infant and child mortality, however. As much as 10% of the historical between-race mortality gap would have been closed if every black man was given a black name. Suggestive evidence implies that cultural factors not captured by socioeconomic or human capital measures may be related to the mortality differential.

The Dynamics of African-American Health: A Historical Perspective

There are many misconceptions about African American health that have subtle and continuing influence on health policy debates. Unfortunately, many of the misconceptions surrounding African American health have an implicit historical dimension, and the usual response for the lack of evidence in support of any myth is that “the data does not exist” to shed full light on the given question. This is unfortunate as there is now a growing body of evidence pertaining to the historical health of the African American population, and this data is currently being used to uncover a number of facts about the historical dynamics of African American health. In this paper, we show that our historical data on the health of African Americans is wholly lacking and at the same time show that one prominent myth about trends in African American health does not stand up to historical investigation. We conclude with a brief note about where this research is headed and what future topics should be explored in African American economic and health history.

Segregation and mortality over time and space

Few studies have been able to measure the evolution of segregation on health disparities or assess whether those disparities existed in rural communities prior to the Great Migration of African Americans to urban centers. We use a newly developed measure of historical racial residential segregation based on individual-level data. The measure exploits complete census manuscript files to identify the races of next-door neighbors. This measure is the first and only measure of historical segregation for rural communities, allowing us to greatly extend the empirical analysis of the effects of racial segregation on health over space and time. Using this comprehensive measure of racial residential segregation, we estimate the historical relationship between racial segregation and mortality. We find that conditional on racial composition, racially segregated environments had higher mortality rates and it was not always the case that the outcomes for blacks were worse than those of whites. These effects of segregation on health differed between urban and rural locations. We conclude by noting how comprehensive measures of segregation can extend the analysis of structural factors in racial health disparities to rural residents and to the historical evolution of health disparities.