If what you suggest is true, then research-oriented institutions with permanent employment, like the Institute for Advanced Study and the Perimeter Institute should be comparatively much more productive than the University Departments similar in size, skills and scope. I wonder if someone measured it.

Richard Hamming, who was a prominent and successful scientist -- qualified to judge academic productivity -- famously argued the reverse. His comment was "The Institute for Advanced Study in Princeton, in my opinion, has ruined more good scientists than any institution has created, judged by what they did before they came and judged by what they did after. Not that they weren't good afterwards, but they were superb before they got there and were only good afterwards "

The explanation is that being in contact with undergrads and grad students forces you to work on and think about a lot of small problems -- and that you're more likely to have a big result if you go looking for small ones, rather than trying to work only on very hard problems.

[Via http://www.cs.virginia.edu/~robins/YouAndYourResearch.html]