The population growth of the United States is well expressed by Reed and Pearl with a logistic equation,
where y is population in millions, and the origin of x is 1870. One of the characteristics of this logistic curve is that its lower asymptote is zero. I may provisionally call this type of curve as simple 1 gistic.
According to Lotka, such a populat'on, which has for an extended period of time been following the logistic law, has a definite pattern. Its demographic characteristics are not fortuitous or capricious, but conform to a type or model determined by the logistic law of growth itself.
To the population growth of Japan since the latter half of the Tokugawa Shogunate era (about 1830) the following equation can with good agreement be fitted,
where the origin of X is 1870. The lower asymptote of this curve is not zero, but a definite value, 29 mill'ons. This type of curve may provisionally be called as complex logistic.
Due to the difference of the lower asymptotes the secular changes of the demographic characteris ics of the complex logistic are quite different from those of the simple logistic. By the same procedure as demonstrated by Lotka, I computed, availing the data of Japan, the demographic characteristics such as the number of births and deaths, the birthrate and the deathrate, the apparent and the true rate of population increaae, the fertility rate of female, the age composition and the average age of population for both simple and complex logistic, and the peculiar changes of these demograghic structures are compared each other.
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