MovieLens

MovieLens is a movie recommendation site producing data sets that are widely used for recommender systems research. The data sets can be obtained from GroupLens.

MovieLens data set statistics.
  Ratings Users Items Density Start End
Set            
ML100K 99.8 k 942 1.68 k 6.30% 1997-09-20 1998-04-22
ML1M 999 k 6.04 k 3.71 k 4.47% 2000-04-25 2003-02-28
ML10M 10.00 M 69.9 k 10.7 k 1.34% 1995-01-09 2009-01-05
ML20M 20.0 M 138 k 26.7 k 0.54% 1995-01-09 2015-03-31
ML25M 25.0 M 163 k 59.0 k 0.26% 1995-01-09 2019-11-21
ML32M 32.0 M 201 k 84.4 k 0.19% 1995-01-09 2023-10-13

Popularity concentration in MovieLens data sets (Lorenz curves).