- 1950 to 195410,159
- 1955 to 19597,521
- 1960 to 196413,402
- 1965 to 196915,437
- 1970 to 19749,551
- 1975 to 19799,260
- 1980 to 19846,590
- 1985 to 19898,426
- 19901,084
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