Older adults tend to show lower preferred walking speeds and higher aerobic demands per distance walked than young adults. It has been suggested that a more sedentary life-style contributes to diminished musculoskeletal functioning, which in turn contributes to poorer economy of motion in the aged and sedentary adults. The purpose of this study was to quantify the speed-aerobic demand relationship during walking for old (greater than 65 yr of age) and young adults and to determine whether physical activity status affects this relationship. Aerobic demands for 30 young and 30 old individuals representing sedentary and physically active groups were measured as the subjects performed treadmill walking at seven speeds ranging from 0.67 to 2.01 m/s. All four age/physical activity groups displayed U-shaped speed-aerobic demand curves with minimum gross oxygen consumption per unit distance walked (ml.kg-1.km-1) at 1.34 m/s. A statistically significant age effect on walking aerobic demand was observed, with old subjects showing an 8% higher mean aerobic demand than the young subjects. This age-related effect was not associated with shifts in the speed at which aerobic demand was minimized or with the preferred walking speed of older individuals falling on a less economical portion of the speed-aerobic demand curve. Rather, it was speculated that declines in force-generating capacity of muscle in the aged may require recruitment of additional motor units and perhaps an additional proportion of less economical fast twitch muscle fibers to generate necessary forces. Physical activity status had no significant effect on walking aerobic demand.(ABSTRACT TRUNCATED AT 250 WORDS)

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We investigated the sensitivity of measures of cognitive ability and socioemotional development to changes in parents' marital status using data from the National Longitudinal Survey of Youth, 1979. We used several scores for each assessment, taken at different times relative to parents' marital transitions, which allowed us to trace the effects starting up to five years before a parent's change in marital status and continuing for up to six years afterward. It also allowed us to correct for the unobserved heterogeneity of the transition and nontransition samples by controlling for the child's fixed effect in estimating the time path of his or her response to the transition. We found that children from families with both biological parents scored significantly better on the BPI and the PIAT-math and PIAT-reading assessments than did children from nonintact families. However, much of the difference disappeared when we controlled for background variables. Furthermore, when we controlled for child fixed effects, we did not find significant longitudinal variation in these scores over long periods that encompass the marital transition. This finding suggests that most of the variation is due to cross-sectional differences and is not a result of marital transitions per se.

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This paper uses data from the National Longitudinal Study of the High School Class of 1972 to analyze whether the percentage of female faculty had an influence on female students' post-undergraduate educational and labor market outcomes. The results show a statistically significant positive association between the percentage of female faculty and the probability that female students would attain an advanced degree. Although the percentage of female faculty had no statistically significant direct effect on labor market earnings, having an advanced degree did have a large, positive impact on earnings.T here is a growing concern that the percentage of female faculty at U.S. colleges and universities is too low. University hiring practices have been influenced by this worry. A recent article in the New York Times (1993) emphasized this issue, and noted that whereas about 20% of faculty at selective four-year colleges and universities are women, the percentage of undergraduate women is more than double that figure. The question arises as to how female students might benefit from an increase in the percentage of female faculty. One view is that female faculty act as mentors and role models for female students, and thus promote their subsequent educational and labor market attainments.Although there is concern in the economics profession about the low percentage of female faculty (for example, Hoffman and Reinganum 1993), economists have published little research on the influence of female faculty on female students' attainments. Much of the discussion about the benefits of female faculty arises in the literature on women's colleges. For example, Tidball (1973, 1976 argued that the "favorable climate" of women's colleges, which includes a relatively high percentage of female faculty, promotes women's postundergraduate educational and occupational attainments. However, given that less than 4% of four-year colleges and universities are women's colleges, and less than 3% of female college students attend women's colleges (Newman 1994), a more