Marginal thinking can be dangerous on a personal level, too.

FORBES: How Economics Can Fix Your Life

But letting deal fatigue block the clarity of thinking around real marginal returns is also not smart.

FORBES: Sunk Costs Don't Matter in Venture, Until They Do

Stewart writes to dispel, as a myth not worth thinking about, the notion that high marginal tax rates in one municipality, state, or a country push the wealthy to move to lower-tax locations.

FORBES: Sorry New York Times, Tax Flight of the Rich Is Not a Myth