THESE WERE THE BEST OF TIMES. David Leonhart says Americans have never been better off than they are today. There's a certain amount of truth to this, but also a great deal of non-truth. I think Brad DeLong lays out the real shape of the situation pretty well.
I would also say that, to me, a lot less hinged on the question of whether or not the average American is better off today than he was 30 years ago than most people seem to think. Conventionally, your more lefty liberals offer a very gloomy account of recent decades while people further to the right have a more sunny view. But it sort of doesn't matter. Implementing, say, a universal health insurance scheme will either improve most people's lives or it won't. If it will improve people's lives we should do it, and if it won't we shouldn't. And so on and so forth down the line for your major progressive policy ideas. I'm a liberal because I mostly think the stuff liberals want to do will improve most peoples' lives. So what does it matter if I say "we're better off than we've ever been and we could be even better off if we adopted all these awesome policies" or "things have been terrible for the past thirty years but we could turn it all around if we adopted all these awesome policies"?
What's needed, politically, is to persuade people that electing progressive politicians will bring them policies that will improve their lives -- winning or losing some argument about how we should understand changes in living standards since the mid-1970s is neither here nor there. After all, nobody, even those most committed to a pessimistic view of the recent past, is actually proposing that we literally turn back the clock and make things just the way they were in 1971.