David Leonhardt's time machine

David Leonhardt: This time machine would start its magic by taking us back almost a decade, to the days when everyone from senior Washington officials to ordinary Americans believed that house prices could never drop. We'd then have a chance to persuade Alan Greenspan and Ben Bernanke, the last two Federal Reserve chairmen, to stop saying that nationwide housing bubbles could not happen and to start cracking down on the wishful-thinking mortgages that were making that bubble possible.

We would also stop by the Treasury Department and Congress and ask them to give some more attention to the fact that incomes were stagnating and many Americans were using their credit cards to pay for higher living standards. Finally, we'd pay a visit Wall Street. We'd go to Lehman Brothers and explain to the bigwigs there why they might not want to be borrowing $33 for every $1 in assets they held. If they didn't listen to us, we'd go see a gentleman named Timothy Geithner, then overseeing the regulators at the New York Fed.

In every case, we would issue an urgent message: The United States economy is in the midst of creating the worst economic excesses since the 1920s. If allowed to continue, those excesses will do enormous damage -- damage that you won't be able to stop once it starts.

This damage, of course, is what we are living through right now. And as much as we all may wish they were an easy fix, there isn't. Financial crises cause spending to be depressed and unemployment to be high -- for years.

Are there steps we can take to mitigate the damage? Absolutely. An aggressive policy response in 2008 and 2009 helped prevent another depression. And a more timid response in 2011 has aggravated the problems.

But the economy was never going to recover quickly from the bubbles. That's why sales -- not just of houses, but of appliances, vehicles and even services like entertainment, are all still far below their pre-crisis levels. They will be for a long to come.

It's too late to prevent the last great financial bubble. It's not too late to ask whether we are taking substantial steps to keep the next bubble from being nearly so bad. Remember: there's always a next bubble.