Unfortunately (or perhaps fortunately) for the humorist in all of us, Justin Wolfers posts to the New York Times' Freakonomics blog, but is not actually an author of the recent Freakonomics sequel, Superfreakonomics.  (If you picked up on my reluctance to appear implicitly favorable toward the Freakonomists in my previous post, it's largely because of what I've read about Chapter 5 of that sequel, on geoengineering and global climate change---see, for example, this.)  Nevertheless, the paper by Wolfers and his Wharton colleague Betsey Stevenson, titled Subjective and objective indicators of racial progress, looks interesting.  A rough summary would be that in the US, black or African-American people's self-reported level of happiness has increased substantially since the mid-1980s.  Although it is still lower, even controlling for other circumstances like average income, than for white Americans, the gap has narrowed.  The overall gap (not controlling for income) has also narrowed, but the narrowing appears not to be due to increases in income, but appears due to other factors;  Wolfers and Stevenson suspect, but have no direct data to indicate this, that it is due to the decrease in racism black people encounter in day to day life.

There's some bad news for some of us in the conclusion to their Section II:

Comparing these various estimates, we find that controlling for measurable differences in the lives of blacks and whites explains about one-third of the black-white happiness gap in the 1970s and much of this is due to the differences in income between blacks and whites. Turning to the trends over time we see that little of the change over time is explained by the controls. In all specifications the black-white happiness gap—measured relative to the standard deviation of happiness—is closing at a rate of about 0.5 per century. However, this relative change is composed of both a decrease in the happiness of whites and an increase in the happiness of blacks; the decrease in the happiness of whites is larger once controls for objective indicators have been taken into account. Finally, while the racial happiness gap remains large, around two-thirds of this can be explained by differences in observable characteristics.

White folks, it seems, have been getting less happy---an effect that is only made more pronounced by controlling for other measurable factors.  Actually, Stevenson and Wolfers (2009) claim that this is mostly due to a decrease in happiness among white women.

Reading the paper is recommended as a look at a simple piece of modern social science research, how it tries to control for potentially confounding effects, and how tricky it is to deduce correlation from causation. (An example of the latter: "one reason that married people report substantially greater happiness in a cross-section is that happy people are more likely than unhappy people to marry (Stevenson and Wolfers 2007)".)