What is the Economic Middle Class?

My lovely wife shared this link with me on Facebook.  I got into a discussion in comments there with a right winger who suggested that $250,000 was a very reasonable estimate for median income in Boston.

As it turns out, median household income in Boston is $51,914, close to the national average, and way below the Mass. State average of $67,950.  But right wingers live in a data-free world, so this is no surprise.

Another contention in comments at that site is that the middle class is undefined and undefinable. Not so.  I define middle class household income as the middle quintile.  This range includes the median and a band around it wide enough to hold 20 percent of the population.  You might wish to concoct your own definition with a wider spread, but you'd better not be asymmetric around the median.  Feel free to use the middle three quintiles, if that is your preference.  But if your of concept of middle class gets very far beyond 50% of the population, you really ought to give more thought to what the word "middle" actually means.

Thinking about all this prompted a look at the various income quintiles.  The data, through 2009, is available at the Census Bureau web site, table 694.  This table provides historical data from 1967 through 2009 on the top income limit for the bottom 4 quintiles, and the bottom income limit for the top 5%, expressed in constant 2009 dollars.

Graph 1 presents this data.  The 3rd quintile - my definition of the middle class - is between the orange line and the yellow line.

In 1967, the threshold for the middle quintile was $32, 848.  By 2009, it had increased by 17% to $38,550.  This is a compounded annual growth rate of 0.38%

In 1967, the top limit for the middle (and threshold to the 4th) quintile was $46, 621.  By 2009, it had increased by 33% to $61,801. This is a compounded annual growth rate of 0.68%.

The threshold value for the fifth quintile increased from $66,481 in 1967 by 80% to exactly $100,000 in 2009.  This is a compounded annual growth rate of 0.98%.

To reach the top 5% required an income of 106,684 in 1967.  By 2009, this had increased by 69% to $180, 001.   This is a compounded annual growth rate of 1.25%.

So my comment sparring partner and the current presidential challenger he seems to support are a bit off base.  $250,000 in household income puts a family well above the 95th percentile.  In fact, that is just enough household income to crack the top 2%.

My ongoing hobby of debunking right wing nonsense aside, the point of this post is mainly to inform.
There are two main observations:
1) While the bottom two quintiles haven't changed much over the decades, entry to the third quintile has crept up a bit; and into higher categories it's moved up a lot.  We recognize this as stagnation in the bottom half and growing inequality in the top half, skewed powerfully to the top.
2) This data set stops in '09, so Obama is outside the discussion.  But we can see that all the way up to the 95th percentile, income growth was dead flat during the Bush administration.  No wonder the 95% percentile feels so poor.

But -- surely, some wealth was generated during those 8 years.  GDP growth was positive at least some of the time.  I wonder where it all went?