Ever wonder why the very rich pay so little in gift and estate taxes, which are intended in part to prevent dynastic wealth from hobbling economic growth? Bloomberg’s Zachary R. Mider had an excellent piece last Thursday that used the Waltons—heirs to the Walmart fortune—as a case study to explain how it’s done.

Reporters who want to understand how the very rich can pass billions to their heirs when the law requires a levy on estates valued at more than $5.25 million ($10.5 million per couple) will get a solid understanding from Mider’s 3,800-word piece, which uses plain English to explain several widely used tax avoidance strategies. (The package also included a handy graphic.)

The techniques have been around for years—some blessed by Congress, others by the courts, all of them subject to very aggressive approaches that can transfer huge fortunes to children and grandchildren while sharply limiting tax liability. (The estate tax is so porous that tax expert George Cooper wrote a book in 1979 called A Voluntary Tax.)

Limiting or stopping these strategies, by the way, is not part of the proposed “reform” of the tax laws being promoted by Rep. Dave Camp, R-MI, and Sen. Max Baucus, D-MT. Given all the concern about red ink, reporters ought to ask Camp and Baucus why closing, or at least tightening up, estate and gift tax loopholes is not front and center in their plans.

The Waltons are not at all unusual in using aggressive techniques to escape taxes, but they have been working to preserve their family wealth for six decades. Walmart founder Sam Walton started his estate planning in 1953, Bloomberg notes.

And practice pays off. As The New York Times reported last fall, the Waltons avoided $31.7 million in federal income tax when they arranged to have a dividend the company would have routinely paid in January of this year, when the tax rate was 20 percent, instead be paid last December, when the tax rate was 15 percent.

Of course, the Waltons are hardly the only family to exploit the law. Mitt Romney acknowledged in writing, for example, in January 2012 that no gift tax was paid on the $100 million trust fund for his five sons. The sons get their income from the trust free of tax because the parents pay it for them, which also reduces the size of their estate and, in effect, passes more wealth to the next generation.

And Forbes ran a piece in August by Ashlea Ebeling about ways to benefit from the charitable gifts described in Mider’s Bloomberg piece. Using a charitable remainder unitrust, or CRUT, for example, avoids capital gains taxes for those with big stock market or other gains, increases current income, and generates an immediate income tax deduction—even though the designated charity may wait decades to get paid and ultimately collect just 10 percent of the donated amount.

One cautionary note: Mider’s stellar story calls the Waltons “America’s richest family.” They may well be, but because of limits on disclosure laws we do not know that for sure. Just as stories about crime rates should always refer to reported crime because we do not know the level of actual crime, so, too, should pieces on wealth include qualifiers such as believed to be, based on disclosure statements, or a similar hedge.

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David Cay Johnston covers fiscal and budget matters for CJR’s United States Project. He is a reporter with 46 years of experience, including 13 at The New York Times; a columnist for Tax Analysts; teaches tax and regulatory law at Syracuse University Law School; and is president of Investigative Reporters & Editors (IRE). Follow him on Twitter @DavidCayJ.