As you might guess, it all depends upon what one chooses to observe.  A new article by Robert Shapiro pulls the pieces apart to show that median household income has not moved much since the 1970s; however, it varies greatly by age group and presidential regime.

http://www.brookings.edu/~/media/Blogs/FixGov/2015/03/shapiro_figure1.png?la=en

For example, 25 – 29 year olds in 1975, 1982, 1991, and 2001 all saw their household incomes rise for at least one decade after those designated dates.  Furthermore, the 1980s and 1990s saw relatively continuous median household income growth for those aged 25-29 at the beginning of each decade with incomes falling since the early 2000s.  Even those 25-29 saw their incomes rise post 2001.

“Shapiro concludes that ‘our current problems with incomes are neither a long-term feature of the U.S. economy nor merely an after-effect of the 2008-2009 financial upheaval.’ Nor are they driven by ‘economic impediments based on gender, race and ethnicity, or even education.’ He identifies two structural causes; globalization and information technologies. But he also asks us to think about what Reagan and Clinton did that the two presidents of the 21st century did not do. ‘The Clinton and Reagan fiscal approaches supported stronger rates of business investment than seen under Bush-2 or Obama. In addition, their support for aggregate demand included public investments to modernize infrastructure, broaden access to education and support basic research and development.’ ”

When pundits discuss the economy in general and “middle class economics” in particular, they should bear the above evidence in mind. As is typically the case, averages hide more than they reveal.