Only 16 percent of Americans live in rural areas, and the quantity is dropping, so naturally the U.S. Department of Transportation proudly announced today that "of the $500 million in TIGER 2012 funds available for grants, more than $120 million will go to critical projects in rural areas."
TIGER is the Transportation Investment Generating Economic Recovery, and the allocations are above. Not only does this give rural areas a share of money disproportionate to their population, but rural America's contribution to the economy is even lower than its population share. What's more, as you can see on the map, a number of the rural grants are going to low-unemployment plains states such as North Dakota (3 percent), Nebraska (3.9 percent), Vermont (5.6 percent), Oklahoma (4.8 percent), and New Hampshire (5 percent).
You see this basic dynamic in all kinds of federal grant programs. Typically any kind of rational grant formula would fail to give money to rural areas in a manner that's consistent with rural areas' strength in the U.S. Senate. Therefore you end up with either implicit or explicit special set-asides for rural areas.