“Of course the big elephant in the room for Rice for many years, is the question of why they have such a small percentage of OOS students compared with most other elite private U’s. Does the admissions office intentionally favor Texas applicants, or does Rice just have a problem attracting top OOS students?”
There’s two obvious reasons for the big in-state enrollment at Rice. There’s no mystery or elephant in the room.
First, Rice was operated as small elite institution primarily serving Houston and Texas for a long long time. It was tuition free to Texans until the mid-1960s. So Rice’s history, brand, alumni base, etc. are way way more TX focused than many of its peer private schools would be. Rice’s lineage is sort of like Cooper Union’s (whose enrollment tilts heavily towards NY-ers).
Second, TX is a huge state. So (similar to California) Texas provides a big pool of highly qualified applicants that can fill a majority of Rice’s seats while keeping the selectivity high. It would be tough for Vandy or Duke to do that by relying primarily on their home state applicant pools.