The variability of fiber type distributions between different regions of the same human muscle is believed to be small, based on the sampling of between two and four sites. The objective of the present investigation was to determine the variability of slow-twitch (ST) and fast-twitch (FT) fiber distributions using a more extensive sampling technique than those previously employed. The soleus, biceps, triceps, and vastus lateralis muscles were excised from each of four young men who had died suddenly. Between 13 and 17 sites were sampled from each of the muscles; 3 transverse areas were then examined within each sample. Fiber type distributions were determined from photographs of sections stained for myofibrillar adenosine triphosphatase at pH 10.3, 10.0, or 4.3. The numbers of fibers counted in the four muscles ranged between a mean of 13,660 and a mean of 21,601. The variability in fiber type distributions observed between sites and areas within a site were statistically greater (P less than 0.01) than could be expected from muscles whose fiber type distributions are equally distributed throughout the muscle. It was concluded that sampling between 3 and 5 sites in the different muscles was necessary to reduce the between-site standard deviation to 5%.

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This paper develops new measures of non-school revenue capacity and environmental costs for Massachusetts cities and towns as the basis for a new municipal aid formula. On the capacity side, we account for the constraints of a tax limitation by estimating them as a function of residents' incomes, and also take account of non-property-tax revenue sources and non-municipal budget obligations. On the cost side, we quantify the effects on local non-school spending of characteristics related to environmental costs, controlling for preferences, effi ciency, and non-school local revenue capacity. Our approach is potentially applicable to other states.

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Abstract:Much of America's promise is predicated on the existence of economic mobility-the idea that people are not limited or defined by where they start, but can move up the economic ladder based on their efforts and accomplishments. Family income mobility-changes in individual families' real incomes over timeis one indicator of the degree to which the eventual economic wellbeing of any family is tethered to its starting point. In the United States, family income inequality has risen from year to year since the mid1970s, raising questions about whether long-term income is also increasingly unequally distributed; changes over time in mobility, which can offset or amplify the cross-sectional increase in inequality, determine the degree to which the inequality of longer-term income has risen in parallel.Using data from the Panel Study of Income Dynamics and a number of mobility concepts and measures drawn from the literature, we examine mobility levels and trends for U.S. working-age families, overall and by race, during the time span . By most measures, we find that mobility is lower in more recent periods (the 1990s into the early 2000s) than in earlier periods (the 1970s). Most notably, mobility of families starting near the bottom has worsened over time. However, in recent years, the down-trend in mobility is more or less pronounced (or even non-existent) depending on the measure, although a decrease in the frequency with which panel data on family incomes are gathered makes it difficult to draw firm conclusions. Measured relative to the overall distribution or in absolute terms, black families exhibit substantially less mobility than whites in all periods; their mobility decreased between the 1970s and the 1990s, but no more than that of white families, although they lost ground in terms of relative income.Taken together, this evidence suggests that over the 1967-to-2004 time span, a low-income family's probability of moving up decreased, families' later year incomes increasingly depended on their starting place, and the distribution of families' lifetime incomes became less equal. Changes in economic mobility are of particular consequence when economic disparities among families are increasing over time, as has been the case in the United States in recent decades. If family income inequality is increasing, changes in the degree to which families move up and down can either offset or amplify longer-term inequality-and loosen or tighten the link between a family's circumstances in any given year and its later outcomes. Other things being equal, an economy with rising mobility-one in which families move increasingly frequently or traverse increasingly greater distances up and down the income ladder-will result in a more equal distribution of lifetime incomes than an economy with declining mobility.We examine time patterns of income mobility for U.S. working-age families between 1967 and 2004, using data from the Panel Study of Income Dynamics (PSID) and a number of mobility concepts and measures, including a m...