52 POPULAR SCIENCE MONTHLY. 



of this paper, viz., can the population of the United States an hundred 

 years hence be predicted within reasonable limits of error? 



During the past century the factors which govern the growth of 

 population have fluctuated enormously; there have been wars and epi- 

 demics; there have been decades in which large numbers of emigrants 

 landed upon our shores and there have been other decades in which 

 emigrants were few; there have been years of plenty and years of want; 

 booms and panics, good times and hard times have had their share in 

 the century which has passed. Yet notwithstanding all these varying 

 conditions, the growth of the population has been a regular and orderly 

 one, so much so that it can be represented by a comparatively simple 

 mathematical equation. Can this equation be trusted to predict the 

 population in the decades which are to come? 



How closely the formula will represent the population of the future 

 will depend, of course, upon the continuance of the same general con- 

 ditions which have held in the past. This does not mean that exactly 

 the same factors are to operate, but that on the whole the change of one 

 factor will be balanced by a change in another, so that in the main the 

 character of the growth manifested during the past century will be con- 

 tinued. A decided change in the birth-rate or a widespread famine 

 would bring out large discrepancies. But on the whole it may be ex- 

 pected that the experience of the last hundred years involves so many 

 varying conditions that the general law of growth which satisfies that 

 period will continue to approximate the development of the popula- 

 tion for a considerable time to come. 



This does not mean that any particular census enumeration of the 

 future will be represented closely, but simply that in the main the com- 

 puted values will follow the general growth of the population. The 

 law of probabilities will lead one to expect at times considerable varia- 

 tions. The preliminary announcements from the Census Office, as 

 given in the daily papers, indicate a result for 1900 of about 75,700,000 

 people, a value considerably below the computed one. This would mean 

 that at this epoch the formula was not representing the actual growth, 

 but does not at all indicate that it will cease to represent the general 

 growth of the succeeding centuries. In any event this method furnishes 

 the most trustworthy estimate which can be made for the future, since 

 it gives the result which is mathematically most probable and which is 

 based on all the data of the past. Carrying forward, therefore, the 

 computation we obtain the following values for the most probable popu- 

 lation of the future: 



Computed 

 Year. Population. 



WOO 77,472,000 



W10 94,673,000 



