142 



The Journal of Heredity 



births, or what is called natural increase, 

 differs from an increase by excess of 

 immigration over emigration, or migra- 

 tory increase, in that it is more likely 

 to carry on into the next generation 

 through heredity the main characteris- 

 tics of the parent stock. Where the 

 group is increased by immigration there 

 is less warrant for supposing that its 

 qualities will be perpetuated. 



My real theme, then, may be phrased 

 as " Differences in the Rates of Natural 

 Increase," a more accurate title than 

 "Differential Fecundity." In addition 

 to defining my subject more exactly, 

 this has an incidental advantage. The 

 fecundity or birth rate of the popula- 

 tion of the United States is unknown; 

 the fecundity of any of the numerous 

 groups into which that population may 

 be divided, with the possible exception 

 of a few states, is likewise unknown. 

 Neither do we know the mortality or 

 death rate of the population of the 

 United States, although we do know the 

 death rate of many states and are 

 rapidly advancing towards a determina- 

 tion of the rate for the entire country. 

 These facts might seem to make a paper 

 on "Differential Fecundity " or "Natural 

 Increase" almost impossible. But if a 

 group is unaffected by migration, its 

 total increase at one date over the 

 number at a prior date, determined from 

 two successive censuses, is a measure 

 of its natural increase. The population 

 of the United States is far from satisfy- 

 ing this condition, yet within it there 

 arc certain groups, e. g., Negroes and 

 Indians, so little affected by migration 

 that we may measitre their natural 

 increase from census returns, though 

 neither their fecundity nor their mor- 

 tality is known. Even for the whites 

 the effort to measure the natural in- 

 crease by allowing for the increase due 

 to immigration is not absolutely fruit- 

 less. 



SCOPE OF THE I'APER. 



My subject, then, assumes that the 

 population can be divided into groups, 

 the natural increa.se of which can be 

 determined and com])ared, and my aim 

 is to review the present state of statis- 

 tical knowledge regarding the natural 



increase of such groups. The American 

 poptilation groups of whose natural 

 increase I shall speak briefly are the 

 white and the Negro races, the native 

 and the foreign born, the several 

 nativity strains among the foreign born, 

 the urban and the rural population. 



Among savage or semi-civilized people, 

 the overwhelming majority of whom live 

 little above the star\'ation point, there 

 is a reciprocal relation between births 

 and deaths. When the deaths increase, 

 the births decrease; when the deaths 

 decrease, the births increase. For 

 example, in European Russia in the 

 famine year, 1892, the deaths exceeded 

 the annual average of the years before 

 and after the famine by more than half 

 a million, and the births in that year 

 fell below the annual average for the 

 years before and after by more than 

 v300,000. Conversely, in such countries 

 a bountiful crop lowers the death rate 

 during the time the food lasts, and 

 raises sharply the birth rate a few months 

 later. Most civilized countries have 

 emancipated themselves from this close 

 dependence upon food and in them no 

 relation can be traced between the crop 

 of grain and the crop of babies. In such 

 countries the only surviving relics of 

 this reciprocal relation between births 

 and deaths are found in cases of war and 

 pestilence. Thus, in Massachusetts, 

 the effect of the Civil War was aijpar- 

 ently more marked in reducing the birth 

 rate than in raising the death rate. 

 The first of the recent e])idcmics of 

 influenza, sweejjing rapidly from Russia 

 over Europe and her outposts in the 

 winter of 1889-90, was the main reason 

 that in nearly every civilized country 

 1890 was a year with a very high death 

 rate. But no attention has been called 

 to the fact that the births in Europe 

 during that year were 200,000 lielow the 

 a\'erage of the preceding five years, and 

 that these losses of life by reduction of 

 the births came in each country from 

 eight to ten months after the mortality 

 from the epidemic reached its height. 



DECLINE IN BIRTH RATE. 



During the last fifty years or less 

 the most marked change in the birth 

 rates and deatli rates of civilized eoun- 



