Juha M. Alho

Migration, fertility, and aging in stable populations

Fertility is below replacement level in all European countries, and population growth is expected to decline in the coming decades. Increasing life expectancy will accentuate concomitant aging of the population. Migration has been seen as a possible means to decelerate aging. In this article, I introduce a stable, open-population model in which cohort net migration is proportional to births. In this case, the migration-fertility trade-off can be studied with particular ease. I show that although migration can increase the growth rate, which tends to make the age distribution younger, it also has an opposite effect because of its typical age pattern. I capture the effect of the age pattern of net migration in a migration-survivor function. The effect of net migration on growth is quantified with data from 17 European countries. I show that some countries already have a level of migration that will lead to stationarity. For other countries with asymptotically declining population, migration still provides opportunities for slowing down aging of the population as a whole.

A competing risks approach to the two-sex problem

The measurement of nuptiality rates is complicated by the fact that a marriage can be attributed both to the woman and the man involved. This is an example of the so called two‐sex problem of mathematical demography. Several theoretical solutions have been proposed, but none has found universal acceptance. We introduce an individual level stochastic model based on competing risks ideas. The model shows explicitly how behavioral factors influence the accuracy of the various models. Although the product model is shown to be the only one that is invariant with respect to the units in which time and age are measured, different behavioral considerations may lead to different definitions of the population at risk. We show that the marriage models are only expected to differ empirically, if the numbers of marriageables vary abruptly in close ages. In an attempt to use data analysis to determine the best fitting risk population, we apply moving averages, approximately polynomial models, and subspace fitting models to Finnish age‐specific marriage data, mostly from 1989. The results are conflicting. Depending on the criterium used, different models provide the best fit. We also study the role of the models in the forecasting of marriages. In some circumstances, an erroneous choice of the population at risk model can be compensated by a particular forecasting method.

Relating changes in life expectancy to changes in mortality.

I address the problem of what can be said of changes in mortality rates, if one knows how life expectancies change. I note a general formula relating life expectancies in different ages to mortality and prove that if mortality changes over time following a proportional-hazard model, then there is a one-to-one correspondence between life expectancy at birth and mortality rates. Extensions and an application of these results to the analysis of mortality change are presented.

Estimation of Exposure Time Distributions

In many demographic analyses, such as the assessment of environmental cancer risks, one may be interested not only in the age-by-state distribution of the population but also in the distribution of the population by time spent in a given state. States can represent geographic areas, marital statuses, labor force participation, or states of epidemiologic exposure. Recursive formulas for the calculation of the distribution of the population according to exposure time are derived under time-invariant state transition rates. Although populations can have identical growth rates and identical age-by-state distributions, they can have very different distributions by exposure time. An application to the analysis of carcinogenic exposure states is given, using data from Finland. The effect of population heterogeneity on the estimated exposure time distributions is studied.

Exposure to Hydrazine and its Control in Power Plants

Abstract The use of hydrazine in power plants was surveyed with a postal inquiry to detect differences in exposure when alternative technical procedures were used in the handling of hydrazine. The exposure level of employees in eight plants was estimated based on the concentration of hydrazine in the air and the potential absorption through the skin. The questionnaire was sent to 288 power plants and 264 were returned, 100 of which used hydrazine. About 500 employees dosed and diluted strong (15% or 35%) hydrazine solution. The dosing was usually done with a pump or an ejector in bigger plants and with a measure in small plants. The airborne hydrazine concentrations in the rooms where hydrazine was handled were: < 0.01–0.06 ppm (mean < 0.02 ppm) for dosing with measure; < 0.01–0.37 ppm (mean 0.12 ppm) for dosing with pump; < 0.01–0.33 ppm (mean 0.09 ppm) for dosing with ejector, tank not closed; and < 0.01–0.04 ppm (mean 0.02 ppm) for dosing with ejector, tank closed and equipped with exhaust. The time-we...