THE FACTS OF LIFE.

Auckland Star, Volume LXVII, Issue 139, 13 June 1936, Page 6 (Supplement)

THE FACTS OF LIFE.

OUR LONGEVITY GAIN. IS EXCESS OF BIRTHS MISLEADING ? STATISTICIANS' OPINION. Pick up Dublin and Lotka's recently published "Length of Life" (Konald) and you discover more about the average man. Dr. Louis I. Dublin is third vicepresident of the Metropolitan Life Insurance Company of New York, and Dr. Alfred J. Lotka is assistant statistician of the same company. Each is well known —Dublin for his many contributions to magazines and his books 011 population, and Lotka for liis "Physical Biology," which broke new ground and which was recommended by the Library Association for the Institute on Intellectual Co-operation of the League of Nations.

Both Dublin and Lotka, like other statisticians,' have done much to acquaint us with the now familiar and agreeable fact that at birth the expectation of life for a man is 59.31 years. When a'male child reaches the age of 10 its further expectation is 55.3 years; at 21 it is 45.21 years. The expectation of life of- women exceeds that of men by 3.52 years at birth and by somewhat lesser amounts in later years.

Thirty years ago the picture was darker. Then the average length of human life (the same thing as the expectation of life- at birth) was 40.07 years. In a hundred years the gain has been of the order of 20 years.

Why the increase? Not one but several answers must lie given. Dublin and Lotka stress improved standards of living and advances in medical and sanitary science.

Especially valuable is the description of "Applications, to Population Problems," which clearly follows the lines laid down by Lotka's "Physical Biology." Years ago Lotka showed that a population in which survival and reproduction follow a fixed age schedule ultimately increases at a definite rate different from that which may prevail at the moment. The existing and transitory age distribution which disturbs the balance between births and deaths gives place to a stable age distribution. - The birth and death rate is then characteristic of the actual mortality and fertility.

The principle was first developed by Lotka and Dublin in a notable article published in 1925, now one of the classics of population studies. What does it mean? That the present excess of births over deaths is misleading. Actually our prevailing rate of reproduction is insufficient in the long run to balance our mortality despite the increased expectation of life.