I love this Wall Street Journal story this morning on how CEOs, despite their rich paydays, often get automatic gains on their retirement plans, while their proles face the whims of the markets.

This is really solid reporting. You always like to see “according to a Wall Street Journal analysis” rather than “according to some study somebody flacked out.” But it’s important to recognize the conceptual ability at work here. Before you do the reporting you’ve got to have the idea, which at bottom is this:

The disparity underscores a fact of life in America’s corporate-pay scene. It’s not just bigger paychecks that have led to a growing wage gap—it’s the different levels of risk that executives and rank-and-file employees face in their retirement plans.

The story benefits from an excellent anecdotal lede:

Jacqueline D’Andrea last year lost more than 60% of the 401(k) savings she built over a decade as a Wal-Mart Stores Inc. manager, she says. The 1.2 million employees in the retailer’s 401(k) retirement plan lost 18% as the market plunged, corporate filings show.

Top executives at Wal-Mart didn’t face such risks. Thanks to a guaranteed 6.6% return, Chief Executive Officer H. Lee Scott Jr. had gains of $2.3 million in a supplemental retirement-savings plan, bringing its total savings to $46.7 million.

This is an interesting glimpse of the glaring disparities between risk at the top and even the relatively high level of an in-store manager. First of all, that 60 percent loss shows the flaws in the 401(k) system, which puts the onus for investing on people who have no idea what they’re doing. Even in 2008, 60 percent is a bad loss. The Dow was down 34 percent last year, while the S&P 500 was down 38 percent. Ms. D’Andrea should have been in index funds, should have been in some cash, and should have been in some bonds.

While the average Wal-Mart employee’s 401(k) was down just 18 percent, I’ll bet you that’s because a good chunk of them had their money in cash because they didn’t know any better. Lucky them. If there’s some consolation for Ms. D’Andrea it’s that even with a 60 percent loss, she didn’t lose that much money. Her account went down to $6,000, implying that she had just $15,000 at the start of 2008. Which doesn’t say much for Wal-Mart’s pay and benefits.

But the CEO, Mr. Scott, is on a fixed-benefit plan. While all the risk of retirement has been shifted onto everybody else, the CEO, who gets paid the most ($31.6 million last year alone), has none. Heckuva system there. This is not a one-off: The WSJ says a quarter of executives saw gains last year, “often” from these types of guaranteed-return benefits. I’d bet that “often” was nearing 100 percent.

Here’s another anecdote, the second of several excellent ones:

Comcast Corp., the cable operator, provides top executives with 12% interest on supplemental savings. This provided Executive Vice President Stephen Burke with gains of $7.4 million in his deferred-compensation account, helping to boost his total retirement savings to $71 million, show corporate filings.

The retirement funds of more than 70,000 workers in the Comcast 401(k) plan lost $649 million, a drop of 28%, filings show. Their average account size by year end was $24,000. The company, which confirmed the calculations, declined to comment.

Finally, this is a good kicker:

But the 48-year-old Henderson, Nev., resident lost her job in May and cashed out. She vows to never join a retirement plan again. “It’s too risky,” she says.

Great work.