2.10 Alfred Lotka - population mathematician

At first, the examination of birth and death rates was often based on simple calculations in which the number of births and deaths was viewed in proportion to the total population. This resulted in a ratio describing the probability of the occurrence of that phenomenon. It could be expressed as a percentage.

The American biologist and statistician Alfred Lotka (1880-1949) gave the decisive impetus for mathematical presentation of population phenomena. He examined the relation between the birth and death rates and the age structure of population. He proved that population growth in the USA has been produced artificially by taking in immigrants. In contrast, natural population growth no longer guarantees the growth of population (in the 1920s) but in the long run the number of population will fall if no immigrants are allowed into the country.

Alfred Lotka based his views on the fact that immigrants are young people who are forming families, which increases the population growth in the area. In contrast, the low birth rate of the original population does not ensure growing population in the longer term.

Irrespective of the size of natural population growth, the age structure of the population would become stable in the future. If natural population growth was zero, age groups would be of the same size year after year. This might be an ideal state for the development of society. Then at least the size of future age groups would be known in advance.

In contrast, if natural population growth increased or decreased, the relative differences between age groups would remain the same. This would also give planners and decision-makers a clear picture of the coming age groups. This is so in theory, but in practice the birth rate has varied strongly and migration has often disrupted the stable development of population structure. The mortality rate has, however, fallen steadily throughout last century, which could even be predicted by mathematical models.

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