It's hard to predict the future, but it's fair to say that WashU has long-term stability. In terms of reputation, you can go back to surveys from 1971 and find that WashU was in the top 10 medical schools. Check out the rankings for yourself: http://bit.ly/1f4AAMK You can see that most of the top 10 back then are still top 10 today. Cornell dropped a bit, but that's it. The sliding from #2 to #6 is, I'm convinced, more a function of changes in USNWR algorithms than actual change in the reputation of the school. If you look at the raw reputation scores only (from surveys of other deans and residency directors nationally), you'll see that WashU has been stable for most of the past decade at about rank 5.
Stability not only describes the reputation of WashU, but also the institution as a whole. 1) The decision-making structures emphasize consensus-building and often result in a more conservative approach in policy (e.g. pass/fail). 2) The financial structure is minimally reliant on tuition, endowment income, and grant funding, and results in maximal security in times of economic recession and sequestration. (Compare against HMS, which is reliant on endowment, and had to beg its affiliated hospitals for special funding during the recession.) 3) There are no earthquakes in Missouri. The ground is stable. 4) That's all I got.
The other factor that adds to stability is the fact that the med school at Wash U is their pride and joy. The university as a whole is certainly well-regarded, but there's no doubt that the medical school is their crowning jewel and they treat it appropriately. The chancellor of the entire university came to our orientation first year and told us as much. The reputation of the medical school raises the profile of the school as a whole (as opposed to places where the opposite is true) so Wash U is very motivated to do what it takes to keep the reputation up.
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