Brad Schiller takes on the "Median Household Income" vs. "Per Capita GDP" question in a far more professional manner than my earlier blogpost -

...The median household income in 2006 was $48,201, just a trifle ahead of its 1998 level ($48,034). That seems to confirm middle-class stagnation.

[However] Demographic changes in the size and composition of U.S. households have distorted the statistics in important ways.

First, we can easily dismiss the notion that the poor are getting poorer. All the Census Bureau tells us is that the share of the pie consumed by the poor has been shrinking (to 3.4% in 2006 from 4.1% in 1970). But the "pie" has grown enormously. This year's real GDP of $14 trillion is three times that of 1970. So the absolute size of the slice received by the bottom 20% has increased to $476 billion from $181 billion. Allowing for population growth shows that the average income of people at the bottom of the income distribution has risen 36%.

..The "typical" household, however, keeps changing. Since 1970 there has been a dramatic rise in divorced, never-married and single-person households. Back in 1970, the married Ozzie and Harriet family was the norm: 71% of all U.S. households were two-parent families. Now the ratio is only 51%. In the process of this social revolution, the average household size has shrunk to 2.57 persons from 3.14 -- a drop of 18%. The meaning? Even a "stagnant" average household income implies a higher standard of living for the average household member.

And while the household composition has been changing, Schiller also notes that the influx of immigration (legal and illegal) changes the "median" far quicker than the "mean" -

Since 1998, the U.S. population has increased by over 20 million. Nearly half of that growth has come from immigration, legal and illegal. Overwhelmingly, these immigrants enter at the lowest rungs on the income ladder. Statistically, this immigrant surge not only reduces the income of the "average" household, but also changes the occupants of the lowest income classes.

...People keep entering the distribution line from the bottom. Even though individuals are moving up the line, the middle of the line never seems to move. Hence, an unchanged -- or even receding -- median marker could co-exist with individual advancement. The people who were at the middle marker before have moved up the distribution line. This is the kind of income mobility that has long characterized U.S. income dynamics.

And yet, as if on cue, the NYT has an OpEd decrying the situation -

...And if the good times have really ended, they were never that good to begin with. Most American households are still not earning as much annually as they did in 1999, once inflation is taken into account.

...The median household earned $48,201 in 2006, down from $49,244 in 1999, according to the Census Bureau. It now looks as if a full decade may pass before most Americans receive a raise.