On Friday, Hillary Clinton continued her clumsy stroll through economic policy with a promise to nearly double the top tax rate on capital gains, from the current 24 percent to as high as 44 percent.

Not only is this a reversal of her position in 2008, but it would also vitiate most of her husband's legacy as a president who presided over a stock market boom.

In an April 2008 debate, former Secretary Clinton said this specifically of the capital gains tax: "I wouldn't raise it above the 20 percent if I raised it at all." At that time, the top capital gains tax rate was 15 percent.

Her logic then was sound. This is one of the very rare taxes for which rate hikes frequently cause revenue to fall, and rate cuts frequently cause it to rise. The reason is that the tax, when set at too high a rate, creates too many additional transaction costs for investors to move their money frequently to more promising areas of the economy. When the rates are cut, those costs are reduced. Investors become more willing to take gains and pay the tax, and the economy benefits because more cash is moved to new businesses and growth areas.

Today, after President Obama's 2013 tax hike, the top capital gains rate stands at nearly 24 percent. This is the context in which she proposes to raise it yet again.

The historical data (available from the Tax Foundation) demonstrate conclusively that — at least in the context of rates within the range of 15-30 percent — the increase in gains that investors take when this tax is cut more than offsets the lower rate.

In 1981, for example, changes to the tax code reduced the effective rate from 28 percent to 20 percent. And in 1982, revenues from the tax increased slightly (by about $48 million) despite the economy entering a brief recession. In 1983, revenues skyrocketed by 50 percent, to $18.7 billion.

Later in Reagan's presidency, the tax reform bill of 1986 included an increase in the capital gains rate to offset large cuts to the income tax rate. But it did not work out as planned because investors' behavior changed. When this went into effect, the amount of revenue raised from the tax fell from $53 billion to $34 billion.

When Clinton's husband signed a capital gains tax cut in 1997, reducing the effective rate from 29 percent to 21 percent, the result was the stock market boom for which many Americans even now remember his presidency. It also rained manna from the heavens upon the IRS. In 1996, the agency had collected just $66 billion from the tax. In the year the tax cut was signed, that amount rose to $79 billion, and, in the two years that followed it, rose to $89 billion and $112 billion. The reason was that between 1996-99, the amount of gains that investors took rose by more than 75 percent.

During 2003, the rate was lowered once again, and the amount of revenue the IRS collected from the tax went from $51 billion in 2003 to $73 billion in 2004, $102 billion in 2005 and $118 billion in 2006.

This is not a difficult concept. The ideal capital gains tax rate for the government to maximize its revenues is a lot closer to the Bush-era 15 percent than it is to the current 24 percent — let alone Clinton's much higher proposal.

Recall that President Clinton spent much of his 2012 speech to the Democratic National Convention boasting about the glory days of his presidency, by then more than a decade past. "What new ideas did we bring to Washington?" he asked. "I always give a one-word answer: Arithmetic."

Voters should note that this "new idea" does not appear to be in the cards if there is a Hillary Clinton administration.