Table 1.
Baseline Demographic Characteristics of the Studied Populations
| Country, region | Population size in 1918, millions of persons | Mean annual birth rate in 1911–1930, births per 1000 persons |
| Denmark, all | 3.03 | 22.8 |
| Copenhagen | 0.66 | 19.3 |
| Rural | 1.72 | 24.2 |
| Norway, all | 2.59 | 22.3 |
| Sweden, all | 5.82 | 27.8 |
| United States, 10 states | 31.20 | 22.4a |
a
Average for 1915–1924. The 10 states included were Connecticut; Pennsylvania; Maine; Massachusetts; Michigan; Minnesota; New Hampshire; New York; Vermont; and Washington, D.C.