THE DECLINING BIRTH RATE 139 
among the thousand [the number investigated] being married. 
None the less it is obvious that the families are not self-perpet- 
uating. The scientific men under 50, of whom there are 261 with 
completed families, have on the average 1.88 children, about 12 
per cent of whom die before the age of marriage. What propor- 
tion will marry we do not know; but only about 75 per cent of 
Harvard and Yale graduates marry; only 50 per cent of the 
graduates of colleges for women marry. A scientific man has on 
the average about seven-tenths of an adult son. If three-fourths 
of his sons and grandsons marry and their families continue to be 
of the same size, a thousand scientific men will leave about 350 
grandsons to marry and transmit their names and their heredi- 
tary traits. The extermination will be still more rapid in female 
lines.” 
From the foregoing data we may draw several conclusions 
regarding the effects of our present differential birth rate. 
1. We are probably losing the elements of our population that 
belong to native American stock. Wherever data have been 
collected sufficient to base a judgment upon regarding the birth 
rate of native Americans, it has been shown that, with our existing 
marriage rate and death rate the birth rate is insufficient to repro- 
duce the population. The increase of our population comes 
mainly from immigrants and the children of immigrants. The 
eugenic effect of this is good or bad according to the qualities of 
the immigrants of foreign born stocks, and this problem cannot 
be solved in any general or off-hand way. 
2. We are losing the elements of our population that have 
achieved success financially, socially, or in the field of intellectual 
achievement. Speaking generally, none of these classes is repro- 
ducing itself. This condition is quite as bad in Europe, at least in 
several countries, as in the United States. It constitutes a very 
serious menace to our present social welfare, and one which is 
striking at the very roots of our civilization. The menace is all 
the more dangerous because its effects do not, like those of war, 
pestilence or famine, obtrude themselves upon our notice. The 
forces for evil that work insidiously are the most to be feared be- 
