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I myself have a long-standing fascination with the Enneagram system and believe it to be the most incisive and encyclopedic theories of human patterns I know. So, yes, I would say there are correlations with career-choice (as with essentially all behavior). I have one more specific comment about job-choice. But first, I'd like to enumerate two important caveats that apply here:
Career choices (like many other important human choices - marriage, politics, etc.) are highly conditioned on background, education, opportunities perceived to be available, etc. - therefore, it is naive to expect overwhelming simplistic correlations. Type Five scientists? Type Eight policemen? Maybe - if one really investigated I suspect there would be evidence that the relative frequencies of these Type-job pairings exceed those expected based on frequencies of the Types in the population under study. But they might not be that much higher - there's just too much variability in our various life paths....
Formal research on the Enneagram is hamstrung in general terms by the lack of a simple, easy objective measure of Enneagram type. Yes, there are various (relatively) cheap-and-easy tests, available on-line and in book-form - but I don't think they are particularly accurate. There's too much at stake psychologically when people are being asked self-report questions, and many of use "game the system" in favor of how we'd like to be seen (even if tend we claim otherwise). This is based on 10+ years experience with hundreds of people coming through a public discussion-group I've run on the Enneagram.
Maybe someday there'll be an Enneagram test based on brainawaves (or whatever). Until then, I'd say, in our time, the better way to get into this system is to read a good book (any of the Risa and Hudson books are good places to start), and look and soberly deeply into yourself if you are so inclined. Then, if you take an abiding interest in the topic, and want to get more involved, try and find an Enneagarm-educted community with sincere people who can help validate (or challenge) your self-assessment. Once securely typed, you can really know how deeply and uncannily this system works in our lives - and curiosities like how the system relates to career-choices may not actually seem as important.
As mentioned above, I do have one more comment specifically on job-choice, however. Based on my own typing skills I once did a survey of a group of 100+ individuals many of whom I know well (my high school class) and attempted to correlate career-choice with Enneagram type. Interestingly, I found that the TYPE-WING actually seemed as strongly typed with career-fields chosen as the MAIN TYPE. Possibly, as individuals who express their main type in so many aspects of our lives, we unconsciously choose career-fields that help express our less-fully-expressed aspects as described by our type-wing. (Just a speculation.) More caveats: (1) TYPE-WINGS may be harder to diagnose properly than the main type itself; (2) I have somewhat different beliefs about what these TYPE-WINGS are than the ones described in the literature.
Sorry for the long-winded answer, that's just the territory as I see it. Please post any replies, and I will attempt to monitor this thread.