&gt; One explanation for that is a contracting economy, but another one is simply that income is becoming more concentrated in the upper end of the distribution.<p>Which is the correct explanation. See, for instance, the income distribution chart [0], from the national-level study that preceded the metro-level study referenced in the NYTimes article.<p>From 1970 to 2014:
The share of aggregate income received by the cohort below the middle (middle, again, is 2&#x2F;3 to double the median income) has gone from 10% to 9% of all income<p>The share received by the middle has gone from 62% to 43% of all income.<p>The share received by the segment above the middle has gone from 29% to 49% of all income.<p>[0] bottom of the two here: <a href="http:&#x2F;&#x2F;www.pewsocialtrends.org&#x2F;2015&#x2F;12&#x2F;09&#x2F;the-american-middle-class-is-losing-ground&#x2F;st_2015-12-09_middle-class-01&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.pewsocialtrends.org&#x2F;2015&#x2F;12&#x2F;09&#x2F;the-american-middl...</a>