656 



POPULAR SCIENCE MONTHLY. 



THE POPULATION OF THE UNITED 



STATES DURING THE NEXT 

 TEN CENTURIES. 



Dr. H- S. Pritchett published in 

 the November number of the Popular 

 Sctence Monthly his estimate of the 

 future population of the United States, 

 based upon the past rates of increase. 

 He found a comparatively simple 

 equation which represented the census 

 enumerations very closely, and, apply- 

 ing that to the future, he finds that the 

 rate of increase, which was 32 per cent, 

 per decade in 1790 and 24 in 1880, will 

 be 13 in 1990, but will not have sunk 

 to less than 3 for another thousand 

 years and will not be zero for an indefi- 

 nite time. He does not seem to have 

 taken into consideration the density of 

 population and what we might call the 

 saturation point, or the maximum 

 population which can be fed. A pop- 

 ulation far below its saturation point 

 will increase rapidly, but when it satu- 

 rates the land there is no increase, and 

 as we approach our saturation point 

 our rate will rapidly diminish to zero. 



We do not know what our satura- 

 tion point is under the present condi- 

 tions of food production; but we pro- 

 duce far more than is needed for our 

 twenty people per square mile. Nor can 

 we estimate our future saturation point, 

 for no one can presume to predict what 

 science will enable us to do in the way 

 of food production, other than what, by 

 present methods, can be forced from the 

 soil. We can only estimate our limit, 

 basing it upon the known densities in 

 countries which have always been pop- 

 ulated to their limit. 



The saturation point rises with civ- 

 ilization just as the saturation point of 

 air for water rises with the tempera- 

 ture. Cultivated land is said to pro- 

 duce 1,600 times as much food as an 

 equal area of hunting land. Denmark, 

 for instance, could support but 500 

 paleolithic people, and when their cul- 

 ture rose to the level of the present 

 Patagonians, 1,000 could exist, and 1,500 

 of those on the level of the natives of 

 Hudson's Bay. In the pastoral stage 



each family requires 2,000 acres, and 

 France could not support 50,000 of such 

 people. For centuries after the Norman 

 conquest the whole of Europe could not 

 support 100 millions, or about 25 per 

 square mile, while now there are 81. 



When civilization is arrested, the 

 saturation point remains stationary. 

 China, for instance, is said to have had 

 400 millions for many centuries. When 

 food can be imported and paid for by 

 manufactured goods, the population can 

 go beyond the saturation point. Great 

 Britain, for instance, is said to import 

 one-third of her food, and her 300 peo- 

 ple per mile is supersaturation. When 

 the countries from which she buys food 

 are populated to the point that they 

 have no surplus for sale, her popula- 

 tion must decrease to the number she 

 can feed, which is now 200 per mile. 

 Should her factories fail through for- 

 eign competition, so that she cannot 

 buy, she will also decrease in popula- 

 tion, just as Ireland has done since the 

 beginning of the last century, when 

 England destroyed Irish industries to 

 strengthen her own. English supersatu- 

 ration is limited only by her power to 

 buy and import. 



America was saturated by savages in 

 pre-Columbian times, and they were 

 constantly at war for more room; but 

 the land has always been far from satu- 

 ration for civilized whites. Though we 

 now export enough food for a large pop- 

 ulation, we cannot produce very much 

 more, for all the useful land is now 

 taken up. Fully 60 per cent, of the 

 desert lands west of the 100th degree of 

 longitude will never have water on it, 

 and that alone will forever prevent us 

 being as densely populated as Europe. 

 Perhaps we can now support fully 125 

 millions, or 34 per mile, a point which 

 Dr. Pritchett calculates we shall reach 

 in 1925, at our present rate. By that 

 time we shall have farms on 10 or 15 

 per cent, of the arid lands, the limit of 

 possible irrigation, and perhaps then we 

 can support 200 millions, the calculated 

 population for 1950; but it is difficult 

 to see how we can feed 500 millions, our 



