By Jeff Reeves

There are many metrics of efficiency these days. But it's undeniable that the lean and mean companies are the ones investors like best.

After all, many companies -- I'm looking at you, UBS (UBS), Bank of America (BAC) and the rest of the financial sector planning layoffs -- have tried to cut their way to profitability lately amid the absence of top-line growth. And while that's not a long-term plan, it certainly can result in nice gains for investors in the near term.

So which players are the most efficient on Wall Street?

I looked at the top 15 stocks by market cap -- spanning a host of industries, including Big Pharma, telecom, consumer goods, retail and technology -- to see if I could spot some trends by dissecting a simple metric: revenue per employee.

It's basic math. Take the revenue, divide by the number of full timers, and you see who's got bloat and who doesn't.

Surprisingly, while some tech stocks are highly profitable, they aren't all minting money at the clip you'd think. And other, seemingly capital-intensive businesses with a host of employees are actually raking in the profits thanks to big efficiencies.

Take a look at the way they shape up:

1. Exxon Mobil (XOM): $5.27 million in revenue per employee
2. Chevron (CVX): $3.84 million
3. Apple (AAPL): $2.34 million
4. Google (GOOG): $1.33 million
5. Microsoft (MSFT): $784,574
6. Procter & Gamble (PG): $664,127
7. Pfizer (PFE): $621,032
8. Johnson & Johnson (JNJ): $550,500
9. Berkshire Hathaway (BRK.B): $549,581
10. AT&T (T): $496,755
11. General Electric (GE): $479,140
12. Wells Fargo (WFC): $338,671
13. Coca-Cola (KO): $325,379
14. IBM (IBM): $244,828
15. Wal-Mart (WMT): $208,003

I was kind of surprised by this ranking. Wal-Mart makes sense -- brick-and-mortar retail with stockers and greeters and cashiers requires a large headcount. Same for Wells Fargo, with its many retail banking outlets.

But what's up with IBM? Or, to a lesser extent, Microsoft? There aren't legions of manufacturing employees or salesmen as at some other companies. What gives? (Microsoft owns and publishes Top Stocks, an MSN Money site.)

I also expected Berkshire to be higher. For giggles I looked at other investment banks -- KKR (KKR) comes in at $5.12 million in revenue per employee, for instance, and Blackstone (BX) is $1.75 million -- and they are much higher. Seems odd that the storied Berkshire Hathaway is so far down the list.

And the biggest shocker, at least to me, was that Big Oil is the best-run industry on this list by a long shot. Better even than Apple, with Exxon Mobil more than doubling the revenue per employee at the tech giant, and Chevron ahead by leaps and bounds.

Equally compelling is that after the top five on this list, the difference is rather insubstantial. You're either in the million-plus club, or you're in the bottom tier. After Microsoft, the revenue per employee in this mega-cap list starts to shrink pretty fast.

Fascinating to me.

This is just one metric, of course, and I'm not sure how "actionable" this is, but it's a metric worth noting. I have long admired the well-run operations of Exxon Mobil, with its steady leadership and long-term outlook in the face of a knee-jerk mentality on Wall Street. But this further cements my belief that one of the very best buy-and-hold investments out there is Exxon Mobil.

Jeff Reeves is the editor of InvestorPlace.com and the author of "The Frugal Investor's Guide to Finding Great Stocks." Write him at editor@investorplace​.com or follow him on Twitter via @JeffReevesIP. As of this writing, he held a long position in Apple.

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