First, though lower income taxes are generally economically better than higher, no recession ever was kicked off primarily by an incremental change in marginal income tax rates.

FORBES: The 'Cost' Of Cuts

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

Your marginal rate is the penalty you pay for earning an incremental dollar of income.

FORBES: Magazine Article

Under pure competition, it is rational for carriers to generate incremental revenue by setting fares only slightly above their marginal cost.

FORBES: Blame Antitrust, Not the Weather, For Travel Woes