Brad DeLong and Paul Krugman are having some back and forth on the problem of secular stagnation and what it would have taken to avoid a prolonged period of high unemployment. I thought I would weigh in quickly since I have a better track record on this stuff than either of them. 

The basic story going into the crash was that we had an economy that was being driven by the housing bubble. This was both directly through residential construction and indirectly through the consumption that followed from $8 trillion of bubble generated housing equity. Residential construction expanded to a record high of more than 6 percent of GDP at a time when demographics would have implied its share would be shrinking. This led to enormous overbuilding, which is why construction hit record lows following the crash. (There was a smaller bubble in non-residential real estate that also burst in the crash.) 

Consumption also predictably plummeted. This is known as the housing wealth effect. (I learned about this in grad school, didn't anyone else?) Anyhow, when people saw their homes soar in value many spent in part based on this wealth. This might have meant doing cash out refinancing, a story that obsessed Alan Greenspan during the bubble years. It might mean a home equity loan, or it might just mean not putting money into a retirement account because your house is saving for you.

In any case, when the $8 trillion in bubble generated equity disappeared so did the consumption that it was driving. You can't borrow against equity that isn't there. This cost the economy between $400 billion and $600 billion (@ 3-4 percent of GDP) in annual consumption expenditures. Between the lost construction and lost consumption, it was necessary to replace close to 8 percent of GDP. The effect of lost tax revenue in forcing cutbacks at the state and local level raised the demand loss by another percentage point or so.

Some of this gap would be filled as excess inventory of housing gradually faded and the vacancy rates came back to more normal levels. We're getting there, but still have some way to go. Some would be filled by a drop in the trade deficit, which now sits at around 3 percent of GDP, compared to a level of almost 6 percent of GDP before the crisis.

The government could fill the remaining gap with additional spending, but our cult of low-deficit politicians is insisting that they would rather keep people from getting jobs, so this ain't going to happen. Low interest rates are of course a good route to spark demand, and if we could lower real rates further with a higher inflation rate, that would be good news. But that one also doesn't seem very promising.

The other part of the demand story would be to make more progress on the trade deficit. This one is not rocket science, a lower dollar means a lower trade deficit (more econ 101). The issue of lowering the dollar is often posed as a matter of getting tough with the Chinese and force them to stop "manipulating" their currency.

We actually don't have to hide in the dark and wait to catch China in the act and then bring them to justice. China very openly maintains its currency at a level that is well below the market rate. They set a target for their exchange rate and they maintain it by buying up massive amount of foreign assets, such as U.S. government bonds. We don't have to catch them in the act, all of this is completely open and involves trillions of dollars of asset purchases.

It is also not a matter of bringing China to justice over the issue. China has found maintaining an under-valued currency to be a useful development strategy, but they also find other policies to be useful to their development strategy, like not enforcing foreign patent and copyrights or not opening their financial markets to companies like Goldman Sachs.

This suggests an obvious path for getting China to allow the dollar to fall against its currency. We simply tell them that we don't care if they enforce Pfizer and Merck's patents or Microsoft's copyrights. We also tell them they don't have to open up their financial markets to Goldman Sachs, J.P. Morgan and the other Wall Street behemoths, we just want them to raise the value of their currency.

Again, this path may not be politically viable either because of the relative power of the drug companies and banks as opposed to tens of millions of unemployed and under-employed workers, but let's at least get the cards on the table. As fans of national income accounting everywhere know, we will not be able to get to potential GDP without large budget deficits as long as we have large trade deficits (assuming no more bubbles).

There is one other item that must be on the full employment agenda especially as we approach the big March 31 deadline for Obamacare. If we reduce the supply of labor we can also get to full employment. Obamacare will be a useful step in this direction since it will give millions of workers the option not to work or to work fewer hours since they will not have to get health insurance through their jobs. This means that parents of young children will be able to spend more time with their kids, people suffering from illnesses or disabilities will be able to rest more and work less, and many older workers will be able to retire early.

There are other ways we can go to accommodate people's needs and thereby reduce the labor supply. For example more paid sick days would be good news, as would be paid family and medical leave. Many state and local governments are leading the way in these areas. Also, some paid vacation would be nice. Four weeks has been the norm in Europe for decades with some countries guaranteeing as much as six weeks of paid vacation. (Yep, it's all in the good book.)

Anyhow, there are always things that can be done. The key point is to first understand where we are. And the most important take away is that millions are suffering now not because we are too poor, but we are too rich. We don't need all the workers we have. This provides enormous opportunities for making people's lives better, if we just had the political will.