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The population dynamics of the voleClethrionomys rufocanus in Hokkaido, Japan

Population dynamics of the gray sided-vole,Clethrionomys rufocanus, in Hokkaido, Japan were described on the basis of 225 time series (being from 12 to 31 years long); 194 of the time series have a length of 23 years or longer. The time series were classified into 11 groups according to geographic proximity and topographic characteristics of the island of Hokkaido. Mean abundance varied among populations from 1.07 to 21.07 individuals per 150 trap-nights. The index of variability for population fluctuation (s-index) ranged from 0.204 to 0.629. Another index for population variability (amplitude on log-10 scale) ranged from 0.811 to 2.743. Mean abundance and variability of populations were higher in the more northern and eastern regions of the island. Most populations, except for the southernmost populations, exhibited significant direct density-dependence in population growth. Detection rate for delayed density-dependence varied among groups from 0% to 22.6%. Both direct and delayed density-dependence tended to be stronger in the more northern and eastern populations. The proportion of cyclic populations was higher in the northern-eastern areas than that in the southern-western areas. There was a clear gradient from the asynchronous populations in southwest, to the highly synchronized populations in the northeast.     

Continuous training in Germany

Using data from the German Socio Economic Panel, I analyze the incidence, financing, and returns to workplace training in Germany for the years 1986 to 1989. Much of this training seems general, and is provided to workers by their employer at no direct cost. While workers typically report larger productivty gains from the training during work hours, such training has lower returns than training undertaken during leisure time. Workers with higher earnings growth seem more likely to participate in training. I deal with this selection problem by estimating models that allow for inidividual level heterogeneity in earnings growth rates. Received: 24 November 1997/Accepted: 27 March 2000     

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