One data point is the netflix rating set from their contest. The system is 1 to 5 stars. The average movie rating was 3.4 in 1998 climbing to 3.8 in 2005. Back

One data point is the netflix rating set from their contest. The system is 1 to 5 stars. The average movie rating was 3.4 in 1998 climbing to 3.8 in 2005. Back to the original point -- if you used a formula with a default rating of 3 it would underestimate low-frequency movies. People don't view movies at random. They try to pick things they will like, which should be reflected in the statistical model.