The density of populations cannot be predicted for an extended period because the factors are so numerous and variable. Nevertheless, the changes are never abrupt and it has been possible in the past to make fairly accurate predictions for fifty years. Elkanah Watson made such a calculation in 1815, and his figures are quoted by Robert Hunter in his work on "Poverty," page 359, from the "Report of the Industrial Commission," Vol. XV, 1901. Unforeseen changes in civilization rendered these predictions wide of the mark after 1865.* In 1830 another estimate was made as to the conditions in 1880, and published in an almanac in 1833. I remember reading this in 1884, and was astounded at the accuracy of the prediction.

We can now calculate what the population will be in 1950, but later conditions are beyond our ken. Most of the predictions have ignored the fact that the percentage of increase lessens as the density increases. For instance, the population in 1900 would have been 100,000,000 if the rate of thirty-five per cent, per decade had continued after 1860, but that rate has been steadily diminishing until it is now somewhere in the neighborhood of sixteen. The safest plan, then, is to draw a curve of the percentage decennial increases and continue it into the future. From this curve we can calculate the total decennial increases and total population, and construct two more curves, which must not show abrupt changes of direction. Such a method gives us the following figures:

*Year

Population

Watson's Estimate

Foreign Immigration for the Decade

1790...........

3,929,214

...

....

1800...........

5,308,483

...

50,000

1810...........

7,239,881

....

70,000

1820...........

9,633,822

9,625,734

114,000

1830...........

12,866,020

12,833,645

143,439

1840...........

17,069,453

17,116,526

599,125

1850..........

23,191,876

23,185,368

1,713,251

1860...........

31,443.321

31,753,824

2,598,214

1870...........

38,558,371

42,328,432

2,314,824

1880...........

50,155,783

56,450,241

2,812,191

1890...........

62,622,250

77,266,989

5,246,613

1900...........

75,559,258

100,235,985

3,687,564

Year

Continental Population

Decennial Increases

Percentage Decennial Increases

1790............

3,929,214

...

...

1800............

5,308,483

1,379,269

35.1

1810............

7,239,881

1,931,398

36.4

1820............

9,638,453

2,398,572

33.1

1830............

12,866,020

3,227,567

33.5

1840............

17,069,453

4,203,433

32.7

1850............

23,191,876

6,122,423

35.9

1860....

31,443,321

8,251,445

35.6

1870............

38,558,371

7,115,050

* 22.6

1880............

50,155,783

11,597,412

30.1

1890............

62,947,714

12,466,467

24.9

1900............

75,994,575

13,046,861

20.7

1905............

*82,567,998

...

.....

1910............

89,195,000

13,200,000

17.4

1920...

102,396,000

13,200,000

14.8

1930............

115,300,000

12,900,000

12.6

1940............

127,500,000

12,200,000

10.6

1950............

138,850,000

11,347,000

8.9

1960............

148,850,000

10,000,000

7.2

1970............

157,600,000

8,780,000

5.9

1980............

165,000,000

7,400,000

4.7

1990............

171,000,000

6,000,000

3.6

2000............

175,500,000

4,500,000

2.6

The following estimates of Mr. C. S. Shane, Geographer of the Census Bureau, have been kindly furnished me by Mr. W. S. Rossiter, the Acting Director:

* Partly estimated.

*  Probably defective.

Year

Bureau of the Census Method

Decreasing Percentage of Increase

1910.............................

89,135,413

90,965,506

1920.............................

102,276,251

107,976,056

1930.............................

115,417,089

127,087,818

1940.............................

128,557,927

148,311,484

1950.............................

141,698,765

171,596,387

1960.............................

154,839,603

196,821,056

1970.............................

167,980,441

223,785,541

1980.............................

181,121,279

252,206,305

1990.............................

194,262,117

281,714,443

2000.............................

207,402,955

311,857,888

The Bureau method is the assumption that the increase each year will be one-tenth of the total increase of the previous decade. It is useless to estimate population as far ahead as 2000, for new factors may bring it to a standstill or even diminish it. Nevertheless, the practical agreement as to population in 1950 shows that we are now in a critical period when the additions to the population are diminishing. The decennial increase which was only 1,333,000 in 1790, and gradually mounted to 13,000,000 in 1900, will be 11,333,000 in 1950, and the decennial percentage increase will have dropped from thirty-five and one-tenth to seven and two-tenths. That is, the facts show that the phenomenal increases, due to the undersaturation of the country, are already a thing of the past. Indeed, Mr. Rossiter reports* that in 1905 some parts of the United States, Iowa, for instance, had actually less population than in 1900. In 1908 there was such a check to immigration and stimulus of emigration of the aliens that there were times when the outflow exceeded the inflow, and the net immigration increase for the year ending October 31, was only 6,298.

The State Censuses of 1905 have been studied by J. F.Crowell,*  and he has discovered a general tendency to arrest of population increase, with here and there remarkable decreases. He shows that it is a phenomenon in both agricultural and manufacturing communities, in none of which has the increase of five years been what was expected.

* The American Review of Reviews, July, 1906. *  Science, December 29, 1905.