"In the last 40 years (between 1967 and 2007), median wages have only gone up US$10000 (from 40k to 50k)."
That figure that you're citing is IN CONSTANT 2003 DOLLARS.
The nominal median household income in 1967, without adjusting for inflation, was $7,260.87. [1] So a "middle class" income has increased from $7,260 to $50,000 in 40 years.
Hopefully this clarification will make the author's nicey-nice spreadsheet make sense now.
That figure that you're citing is IN CONSTANT 2003 DOLLARS.
The nominal median household income in 1967, without adjusting for inflation, was $7,260.87. [1] So a "middle class" income has increased from $7,260 to $50,000 in 40 years.
Hopefully this clarification will make the author's nicey-nice spreadsheet make sense now.
[1] http://www.census.gov/hhes/www/income/data/historical/househ...