[Rain Man]

Here are the latest 2006 estimates from the Bureau of the Census. (The number of households seems too small, but I'm too lazy to check.)

Total:	HH in Category	% in Category	HH in Category OR Below	% in Category OR Below
Less than $10,000	8,898,696	8.0%	8,898,696	8.0%
$10,000 to $14,999	6,639,877	5.9%	15,538,573	13.9%
$15,000 to $19,999	6,222,117	5.6%	21,760,690	19.5%
$20,000 to $24,999	6,499,511	5.8%	28,260,201	25.3%
$25,000 to $29,999	6,162,001	5.5%	34,422,202	30.8%
$30,000 to $34,999	6,284,821	5.6%	40,707,023	36.5%
$35,000 to $39,999	5,733,333	5.1%	46,440,356	41.6%
$40,000 to $44,999	5,699,321	5.1%	52,139,677	46.7%
$45,000 to $49,999	5,078,803	4.6%	57,218,480	51.3%
$50,000 to $59,999	9,465,003	8.5%	66,683,483	59.7%
$60,000 to $74,999	11,756,886	10.5%	78,440,369	70.3%
$75,000 to $99,999	13,214,551	11.8%	91,654,920	82.1%
$100,000 to $124,999	7,933,973	7.1%	99,588,893	89.2%
$125,000 to $149,999	4,230,233	3.8%	103,819,126	93.0%
$150,000 to $199,999	3,981,276	3.6%	107,800,402	96.6%
$200,000 or more	3,817,000	3.4%	111,617,402	100.0%

This implies that, according to raw stats, the "middle class" should radiate outward from a household income of a little under $50,000. The middle two quartiles are going to encompass a range from about $25,000 to about $82,000 in household income, which is a pretty broad spread. The middle three quintiles would cover a bigger range from about $20,000 to about $95,000.

Using this universe, I would probably define it more narrowly as the middle third of households - $33,000 to $73,000 or so.

However, recall that there are all types of households in the country - single young people, elderly widows, empty nesters, DINKS, and others. Politicians like to pander to the traditional American image of a household that includes a sweater-wearing father, pearl-and-high-heel-wearing mother, football-playing son, and tight-cheerleader-sweater-and-short-cheerleader-skirt wearing daughter.

Those traditional family households are different, with much higher incomes. Here's their information:

Married-couple households with children under 18.

	HH in Category	% in Category	HH in Category OR Below	% in Category OR Below
Less than $10,000	363,901	1.5%	363,901	1.5%
$10,000 to $14,999	396,082	1.6%	759,983	3.1%
$15,000 to $19,999	553,348	2.3%	1,313,331	5.4%
$20,000 to $24,999	727,654	3.0%	2,040,985	8.5%
$25,000 to $29,999	804,576	3.3%	2,845,561	11.8%
$30,000 to $34,999	952,683	3.9%	3,798,244	15.7%
$35,000 to $39,999	968,108	4.0%	4,766,352	19.7%
$40,000 to $44,999	1,058,847	4.4%	5,825,199	24.1%
$45,000 to $49,999	1,068,090	4.4%	6,893,289	28.5%
$50,000 to $59,999	2,246,312	9.3%	9,139,601	37.8%
$60,000 to $74,999	3,313,612	13.7%	12,453,213	51.6%
$75,000 to $99,999	4,354,664	18.0%	16,807,877	69.6%
$100,000 to $124,999	2,843,333	11.8%	19,651,210	81.4%
$125,000 to $149,999	1,522,822	6.3%	21,174,032	87.7%
$150,000 to $199,999	1,465,501	6.1%	22,639,533	93.7%
$200,000 or more	1,510,052	6.3%	24,149,585	100.0%

Their "middle class" radiates outward from a figure that's probably around $74,000. Their middle two quartiles range from $46,000 to about $110,000. Their middle three quintiles range from about $40,000 to about $120,000. Their middle one-third ranges from about $55,000 to about $95,000.

I would wager that the "traditional households" help define the middle class more so than all households, even though I think all households should be considered.