A country doubles the share of its young people entering university and finds the odds ratio between class origins almost unchanged. How can both facts be true at once?

C. Rates rose across all origins whilst relative gaps persisted, as expansion adds places without altering relative advantage.

This is the education version of the mobility myth. More places mean more people from every origin arrive, so absolute participation rises everywhere; the odds ratio moves only if the origin effect at that transition weakens. Where advantaged families take up the new places first, the ratio can hold almost exactly steady while the headline participation figure doubles.