Power Couples: Changes in the Locational Choice of the College Educated, 1940-1990

The rise of the dual career household is a recent phenomenon spurred by the increase in married women's labor force participation rates and educational attainment rates. Compared to traditional households these households must solve a colocation problem. This paper documents trends in locational choice between large and small metropolitan areas and non-metropolitan areas by household type from 1940 to 1990. We find that college educated couples are increasingly concentrated in large metropolitan areas and attribute at least half of this increase to the growing severity of the colocation problem. We also find that the relative returns for a college-educated couple of being in a large relative to a small city have increased across decades. Our results suggest that because skilled professionals are increasingly bundled with an equally skilled spouse, smaller cities may experience reduced inflows of human capital relative to the past and therefore become poorer. We examine how the relationship between rankings of university graduate programs and city size has changed between 1970 and 1990 to provide suggestive evidence on the importance of city size to firms' ability to attract the best workers.

Shame and Ostracism: Union Army Deserters Leave Home

During the Civil War not all men served honorably and this was known by everyone in their communities. We study how shame and ostracism affect behavior by examining whether men who deserted from the Union Army, and who faced no legal sanctions once the war was over, returned home or whether they moved and re-invented themselves. We build a unique panel data set that provides us with a control group for deserters because we can identify men who deserted but then returned to fight with their companies. We find that, compared to non-deserters and returned deserters, deserters were more likely to move both out of state and further distances. This effect was stronger for deserters from pro-war communities. When deserters moved they were more likely to move to anti-war states than non-deserters. Our study provides a rare test of the empirical implications of emotion. While both shame and ostracism would push deserters out of their home community, we find no evidence that deserters faced economic sanctions.

Cowards and Heroes: Group Loyalty in the American Civil War

What motivated men to risk death in the most horrific war in U.S. history when pay was low and irregular and military punishment strategies were weak? In such a situation creating group loyalty by promoting social capital is of paramount importance and in the Civil War was the cement of both armies. We find that individual and company socio-economic and demographic characteristics, ideology, and morale were important predictors of group loyalty in the Union Army. Company characteristics were more important than ideology or morale. Soldiers in companies that were more homogeneous in ethnicity, occupation, and age were less likely to shirk.

Changes in the Value of Life: 1940-1980

We present the first nation wide value of life estimates for the United States at more than one point in time. Our estimates are for every ten years between 1940 and 1980, a period when declines in fatal accident rates were historically unprecedented. Our estimated elasticity of value of life with respect to per capita GNP is 1.5 to 1.7. We illustrate the importance of rising value of life for policy evaluation by examining the benefits of improved longevity since 1900, showing that the current marginal increase in longevity is more valuable than the large increase in the first half of the twentieth century.

Understanding the Decline in Social Capital, 1952-1998

We evaluate trends in social capital since 1952 and assess explanations for the observed declines. We examine both social capital centered in the community and in the home and argue that the decline in social capital has been over-stated. Controlling for education, there have been small declines in the probability of volunteering, larger declines in group membership, and still larger declines in the probability of entertaining since the 1970s. There have been no declines in the probability of spending frequent evenings with friends or relatives, but there have been decreases in daily visits with friends or relatives. Rising community heterogeneity (particularly income inequality) explains the fall in social capital produced outside the home whereas the rise in women's labor force participation rates explains the decline in social capital produced within the home.

Superconducting applications in propulsion systems. Magnetic insulation for plasma propulsion devices

The purpose of this paper is to review the status of knowledge of the basic concepts needed to establish design parameters for effective magnetic insulation. The objective is to estimate the effectiveness of the magnetic field in insulating the plasma, to calculate the magnitude of the magnetic field necessary to reduce the heat transfer to the walls sufficiently enough to demonstrate the potential of magnetically driven plasma rockets

Forging a New Identity: The Costs and Benefits of Diversity in Civil War Combat Units for Black Slaves and Freemen

By the end of the Civil War, 186,017 black men had fought for the Union Army and roughly three-quarters of these men were former slaves. Because most of the black soldiers who served were illiterate farm workers, the war exposed them to a much broader world. The war experience of these men depended upon their peers, their commanding officers, and where their regiment toured. These factors affected the later life outcomes of black slaves and freemen. This paper documents both the short run costs and long run benefits of participating in a diverse environment. In the short run the combat unit benefited from company homogeneity as this built social capital and minimized shirking, but in the long run men's human capital and aquisition of information was best served by fighting in heterogeneous companies.

Detection thresholds of macaque otolith afferents

The vestibular system is our sixth sense and is important for spatial perception functions, yet the sensory detection and discrimination properties of vestibular neurons remain relatively unexplored. Here we have used signal detection theory to measure detection thresholds of otolith afferents using 1 Hz linear accelerations delivered along three cardinal axes. Direction detection thresholds were measured by comparing mean firing rates centered on response peak and trough (full-cycle thresholds) or by comparing peak/trough firing rates with spontaneous activity (half-cycle thresholds). Thresholds were similar for utricular and saccular afferents, as well as for lateral, fore/aft, and vertical motion directions. When computed along the preferred direction, full-cycle direction detection thresholds were 7.54 and 3.01 cm/s(2) for regular and irregular firing otolith afferents, respectively. Half-cycle thresholds were approximately double, with excitatory thresholds being half as large as inhibitory thresholds. The variability in threshold among afferents was directly related to neuronal gain and did not depend on spike count variance. The exact threshold values depended on both the time window used for spike count analysis and the filtering method used to calculate mean firing rate, although differences between regular and irregular afferent thresholds were independent of analysis parameters. The fact that minimum thresholds measured in macaque otolith afferents are of the same order of magnitude as human behavioral thresholds suggests that the vestibular periphery might determine the limit on our ability to detect or discriminate small differences in head movement, with little noise added during downstream processing

Maximizing decision rate in multisensory integration

Effective decision-making in an uncertain world requires making use of all available information, even if distributed across different sensory modalities, as well as trading off the speed of a decision with its accuracy. In tasks with a fixed stimulus presentation time, animal and human subjects have previously been shown to combine information from several modalities in a statistically optimal manner. Furthermore, for easily discriminable stimuli and under the assumption that reaction times result from a race-to-threshold mechanism, multimodal reaction times are typically faster than predicted from unimodal conditions when assuming independent (parallel) races for each modality. However, due to a lack of adequate ideal observer models, it has remained unclear whether subjects perform optimal cue combination when they are allowed to choose their response times freely.
Based on data collected from human subjects performing a visual/vestibular heading discrimination task, we show that the subjects exhibit worse discrimination performance in the multimodal condition than predicted by standard cue combination criteria, which relate multimodal discrimination performance to sensitivity in the unimodal conditions. Furthermore, multimodal reaction times are slower than those predicted by a parallel race model, opposite to what is commonly observed for easily discriminable stimuli.
Despite violating the standard criteria for optimal cue combination, we show that subjects still accumulate evidence optimally across time and cues, even when the strength of the evidence varies with time. Additionally, subjects adjust their decision bounds, controlling the trade-off between speed and accuracy of a decision, such that they feature correct decision rates close to the maximum achievable value