- 1960 to 196414,164
- 1965 to 196916,178
- 1970 to 197410,158
- 1975 to 19799,784
- 1980 to 19846,869
- 1985 to 19898,750
- 19901,307
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