The exact shape of the curve is subject to discussion, but the point of diminishing marginal utility is that, as you get more and more money, the increment in utility for each extra dollar diminishes.

这条曲线的确切形状还有待讨论,但是边际效用递减规律的重点在于,你得到的钱越多,每额外的一美元的增长效用会相对减小

耶鲁公开课 - 金融市场课程节选

Low tax rates make it easier to get to the point of diminishing marginal utility from extra work and incremental investment risk.

FORBES: How I Know Higher Taxes Would Be Good For The Economy

The sticking point was the marginal rate of the income tax.

FORBES: Tim Geithner Meekly Phones In Tax Reform

The study suggests that each reduction of one percentage point in the marginal tax rate could increase the number of new businesses by as much as 2%.

WSJ: Do Angel Investors Deserve Tax Credits to Invest in Small Businesses?