...As banks, retailers, and consumer products companies continue their well-documented scramble to court so-called Millennials, the lifestyle choices of this newly adult generation are having a profound effect on a lesser-explored area of the U.S. economy: infrastructure. In the simplest terms, Millennials (which Pew Research defines as Americans born from 1982-2000, and called Generation Y by some) are driving less than older motorists did when they came of age--and when they do get behind the wheel, they are generally in smaller, more fuel-efficient cars. This, in turn, has curbed revenues from the federal gasoline tax, the primary source of funding for the Federal Highway Trust Fund, which is the backbone of the country's surface transportation infrastructure. This drop in funds available to construct and repair the country's infrastructure could, in Standard & Poor's Ratings Services' view, weigh on growth prospects for U.S. GDP, as well as states' economies, and, in some cases, where...