Although this monograph is intended to be mainly an analysis of census data on fertility, it would be incomplete without some use of the extensive and valuable birth registration data collected by the States and compiled on a national basis by the National Office of Vital Statistics. Most of the measures of fertility which have been developed thus far, including the relatively new field of cohort fertility, are derived from birth registration data.
A series of national estimates of annual births for the period from 1909 to 1934, prepared by P. K. Whelpton and published by the National Office of Vital Statistics, is used in some of the tables below. The series incorporates carefully prepared estimates for States not in the Birth Registration Area and also incorporates adjustments for underregistration. The Birth Registration Area was established in 1915, with ten States and the District of Columbia. Other States were admitted to the Area when their registration systems attained a required degree of reliability.1 It attained nationwide coverage in 1933 with the admission of Texas. The tables make use of the National Office of Vital Statistics underregistration- corrected data for years from 1935. Attention is also called to the existence of other estimates of births and birth rates which various writers have prepared and published since at least 1806.2 Thus, at least a rough idea can be obtained of the magnitude and trends of births and birth rates in the United States for many years before the completion of the Birth Registration Area.
Crude birth rates. At the beginning of the twentieth century, the United States had an estimated annual birth rate of 32 births per 1,000 inhabitants. The birth rate declined in irregular fashion, from about 30.0 in 1.909 to 18.4 in 1933 (table 11). It dipped during World War I, recovered to a postwar high in 1921, and then declined fairly steadily. Monthly data indicate that the birth rate reached its lowest level in September 1933, about ten months after the presidential election in November 1932, which____________________