How many people total in the FO around the world?

How many people are there, total, in "front office" roles?

This has been bugging me for a while, and I apologize if it's already been discussed at length here (I looked and couldn't find an answer), but I wanted to get some other people's input.

I feel like I've seen estimates in the press of more than 240,000 people on "Wall Street" in NYC by itself (though I can't find one right now...). You also here reports of "thousands" of bankers and traders fired. These numbers, and the implications for total industry size, seem very high to me based on my limited experience.

My estimated range is that there are probably between 100,000-500,000 people in FO globally, with the upper middle part of that range being the most likely (300,000-400,000). I am soliciting others input precisely because I think this may be wrong, so if anyone disagrees with my work below please comment.

Let's start with the buyside:

Total HF industry AUM: roughly $2 trillion, total HFs: less 10,000 based on most reports.
Total HF industry FO employment (estimate): 50,000 (figure 5 per firm?).

Total PE\VC employment: 73,000 according to this report (http://www.preqin.com/docs/samples/2011_Preqin_Pr…). Not vouching for credibility of that report...but it seemed sane to me, mostly in relation to the HF number. Let's round to 75,000.

Sell Side:
Just to shortcut, say 2x as many as buyside globally, for an estimate of about 250,000. As a a sanity check, this is roughly as many people as the press reports I thought I read suggested work in the industry in NYC, so this may be very wrong.

On the other hand, I think global analyst classes aren't likely to be much more than 10,000-20,000 across all banks and I think this is roughly proportional with an industry head count of 250,000.

So my total point estimate is 375,000 globally. I'd be a little surprised to learn I'm off by more than an order of magnitude, but I don't have a great deal of confidence in this number by itself.

If you restrict this to "high finance" (i.e. people in HFs & PE with $X billion AUM, BB banks, elite boutiques), I'm guessing we'd probably get closer to 100,000. I figure 20,000 total at most in brand name PE and HFs; maybe 4x that at brand name banks in IBD and S&T combined. This kind of proportionality seems vaguely consistent with buy side to sell side "conversion" rates I've heard mentioned here.

What, if anything, did I do wrong? Other estimates? Other intuition on industry size?