Three Rulers, One Dataset

25 years, annotated by its own timestamps

Ratings per year. The shaded bands are the three instruments; the marks are events the timestamps confess: the 1997 seam (a 48-day hole between the imported EachMovie data and native MovieLens), the Nov 1999 press wave (Gladwell, Nightline, Ebert: a 10× jump in one month), the 2003 half-star switch, and the 2014 relaunch.

The old ruler flattered bad movies

822 movies have 200+ ratings in both whole-star eras. Band them by how the native era scores them, and compare the same films across eras: a clean staircase. Movies the native era calls terrible looked 0.8 stars better under the imported instrument; the beloved barely moved. Consistent with the six-to-five scale conversion squeezing the bottom, and with 1996 audiences meeting these films as new releases. Either way: averages that cross 1997 inherit it.

Small n at the extremes (3 and 29 movies); the finding rests on the monotonic gradient across all seven bands, not on any single band.

The harsh minority owns the average

Heavier raters score lower, and they cast most of the votes. The dot is each group's average rating; the right column is their share of all 25M ratings.

Users under 20 ratings are excluded by the sample's own design; the casual web visitor does not exist in this dataset at all.

“Best movie” is a settings menu

855 movies hold a perfect 5.0; 820 of them earned it from exactly one person. Honest rankings publish the floor next to the winner. Most-rated is a different question: Forrest Gump, 81,491 — nine ratings ahead of Shawshank.

What the audit checked

• Every movie has at least one rating or tag — true for all 62,423
• One rating per (user, movie) pair — true across 25,000,095 rows
• Movie ids unique in every table that claims it
• All 98 same-title movie pairs are genuinely different films (checked via IMDb ids)
• The documented genre list is stale: IMAX missing from it, Children's vs Children

Also on the books: three timestamp scars (three ratings on one 1995 second, the 48-day 1997 seam, and 506 accounts all terminating on the morning of May 22, 1998, the signature of an undocumented batch migration).