House Ways and Means Chairman Kevin Brady, R-Texas, left, and Speaker Paul Ryan, R-Wisc., joined by members of the House Republican leadership, introduce tax reform legislation Nov. 2, 2017, in Washington, D.C.

One of the promises of the GOP tax cuts is that Americans will spend their windfall from lower taxes, which will drive up consumption and job growth.

But a new survey shows that American millionaires, who could get the biggest benefits, don’t plan to spend. Most plan to save and invest the gains, which would limit the short-term impact of the tax cuts.

According to the CNBC Millionaire Survey, more than three quarters of millionaires who expect a tax cut this year will either invest or save their extra income.

The biannual survey was conducted by the Spectrem Group in April and polled 750 Americans nationwide with $1 million or more of investable assets.

Wealthier millionaires, or those worth $5 million or more, are even more likely to sock away their tax savings. Nearly two-thirds of those multimillionaires plan to invest their savings, while another 24 percent plan to save it. Only 4 percent of them plan to spend it.

Analyses of the tax plan show that more than half of the benefits will go to the top 5 percent of American earners. This group gets the biggest gains on both a dollar and percentage basis. The top 0.1 percent of earners will get an average tax cut of $193,380.

When asked who would benefit the most from the tax cuts, most of the respondents in the CNBC Millionaire Survey said shareholders and executives of companies. Only 8 percent of millionaires said workers would see the biggest benefits.

Still, the millionaires do believe the tax cuts will be good for the economy and jobs. More than half say the cuts will create more jobs. But the views were split by party. More than 80 percent of Republican millionaires said the tax cuts will create jobs and help the economy, compared with less than a third of Democrats.