One issue this poses is that analysis of political issues in terms of “income” quartiles can get pretty misleading. A married couple where dad earns $65,000 a year and mom works part time bringing home $15,000 a year is in the fourth quartile of the American income distribution. A 70 year-old widower whose $2 million in savings bring him an annual income of approximately $80,000 is also in the fourth quartile. But their policy-relevant economic interests are unlikely to have very much in common since in reality their financial situations are entirely dissimilar.
Yglesias had it right (in this quote, I didn’t read his whole post): The political jockeying over “income” can get pretty misleading. Yes, that’s exactly right, and everybody who is going to think through such issues had better be aware of the kind of complications Yglesias (and Sumner in past posts) brings up.
But that doesn’t mean income is “meaningless.” I responded in the comments:
Why stop at “income” Scott? These 388 examples all show that numbers are meaningless. Look at how much people are confused by the use of numbers! Meaningless. What the heck is “80,000″ anyway?
(For a more serious defense of the economic concept of income, see this article.)