POPULATION OF THE UNITED STATES 



387 



we obtain the following forecasts : 



1970 209.7 millions 



1980 234.4 



1990 260.4 



2000 287.8 



2500 3,443.8 



3000 10,099.8 



Since one of the factors used in the formula is a square, it is notice- 

 able that the increase is quite a rapid one as the years go on. In the 

 year 2270, which is not so very remote, the estimate is 1,557 millions, 

 which is about the population of the globe at the present clay. The 

 predictions reached by this formula are somewhat smaller than those 

 given by the formula of Dr. Pritchett in the article referred to. An 

 interesting point in the curve is noticed for the year 1870. It will be 

 observed that the population for this year differs more widely from that 

 of the predicted population than that for any other year. This is 

 probably due to two causes. In the first place, the effects of the civil 

 war are shown in the reduction of the population, and, secondly, it is 

 probable that the census of 1870 was not so accurately taken as that of 

 any other decade. This latter reason is given by Mr. Eobert Porter in 

 the Census Bulletin No. 12, 1890. 



There is another method of forecasting the census, which depends 

 upon reported estimates of the population in various centers. " The 

 World Almanac," for example, secures the best available data from 

 government and other officials, and each decade estimates the census 

 which is to be taken. In January, 1900, this estimate was 79.4 millions, 

 while the census enumeration showed 76.3 millions. This was about 

 4 per cent, too high. In January, 1910, the estimate is given as 92.3 

 millions. If this is reduced in this ratio, it gives a result of 88.8 

 millions for the year 1910. 



In conclusion, it may be stated that the results of empirical formula?, 

 unlike those of the mathematical formula?, are never perfectly reliable 

 or correct. It is, therefore, impossible to predict the population for 

 1910 with any such degree of certainty as one can predict the free fall 

 of a body in a given interval of time. It is to these empirical formula?, 

 however, that science owes much of its progress, and the governments 

 of civilized countries are spending thousands of dollars in order to 

 bring the constants in these various formula? a little nearer the truth. 

 In its application to the problem before us, it may be stated that if 

 the population for 1910 shall be found to conform to the general trend 

 of increase in the population since the first census was taken, we may 

 feel certain that it will come out about 89.7 millions. If, on the other 

 hand, it shall be found to conform more nearly to the growth made in 

 the last few decades, it will be about 91.3 millions. Of course, there 



