- 1930 to 19344,820
- 1935 to 19396,910
- 1940 to 19446,714
- 1945 to 194911,265
- 1950 to 195410,827
- 1955 to 19598,226
- 1960 to 196413,878
- 1965 to 196915,850
- 1970 to 19749,896
- 1975 to 19799,588
- 1980 to 19846,803
- 1985 to 19898,657
- 1990 to 19945,108
- 19952,239
The preservation of the Duke University Libraries Digital Collections and the Duke Digital Repository programs are supported in part by the Lowell and Eileen Aptman Digital Preservation Fund