Internal migration within the United States continues to transform both the magnitude and composition of population at all geographic scales. During 1994 ‐ 1995, the majority of counties gained both people and income, largely as a consequence of net outmigration by higher income migrants from the nation's most populous cities. Regionally, net gainers of both people and income included counties in the West and South as well as other areas renowned for environmental amenities. Spatially, net migration flowed down the urban hierarchy from large central cities to adjacent suburbs which, in turn, exported migrants to exurban areas. Large cities tended to exchange migrants with nearby counties as well as other large cities. Migration patterns such as these are contributing to spatial deconcentration and economic disparity.

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Interstate migration exchanges in the United States are temporally and spatially transitory. Both the early and mid‐1980s exhibited significant fluctuations in the origins and destinations of U.S. migrants, while the late 1980s and early 1990s were even more unstable. Regions once favored by interstate movers such as the West and the South, while remaining attractive, showed evidence of declining favor in the early 1990s. Meanwhile, numerous states in the national interior regained their attractiveness, including several that gained net migrants for the first time in decades. California exhibited a major turnaround in its migration, perturbing the entire U.S. migration system.

The spectrum of Barkhausen noise has been measured in iron and analysed using signal analysis techniques. The results suggest that the mean duration of the voltage pulses caused by the domain reversals is less than 5 x 10-5 s and that a domain reversal triggers other domain reversals with a time delay normally of 1 to 2 ms. Delays of up to 10ms do occur. The results agree with those obtained by Sawada. The technique allows detailed information of the dynamic nature of domain reversals to be obtained quickly and with little sample preparation.

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