[Secular trends of demographic parameters].

The aim of this paper is to describe the secular changes of selected demographic parameters and to investigate the possible causes for such changes as well as the biological relevance. We took into account the following parameters: population density, mean live expectancy, average age at marriage of until then unmarried persons, rate of live births, and number of children per woman. The results show that the population density (global and in Germany) especially in the twentieth century increased dramatically. We found a striking increase of life expectancy in Germany. Essential causes are rapid decreases in infant and maternal mortality. Since the 80s of the twentieth century the average age at marriage of until then unmarried persons as well as the number of single mothers show a permanent increase. Generally, the average age of mothers increased (for live and legitimate births). In the past 150 years we found a decrease in fertility rates in Germany. The registered demographic parameters show temporal and regional variations. These differences, especially between East Germany and West Germany, are emphasized.