Well, well.It's suddenly become very hip to believe in a V-shaped recovery, and to slam the pessimists for not knowing their history. As Jim Grant argued yesterday in the Wall Street Journal, the severity of the slump predicts the severity of the recovery -- it's just like physics!

But economics isn't physics. And don't worry about not knowing your history, because economics isn't history either.

Here's why we're not in for a v-shaped recovery.

First, the pax economica that preceded the current slump was artificial. Large swaths of the economy had stopped doing anything productive, while the rest of the economy was buoyed by rising home values that allowed for spending on a level that was disconnected from what people were actually bringing in via income. Of course, you know this part of the story, but the key is that this is meaningfully different than the situation heading into previous economic slumps.

The other reason why we're not in for a "V" is that the economy, even without the credit-collapse, is still in the midst of violent changes in the economy. New technology and new business models are uprooting old businesses (whether it's media, manufacturing, or commercial real estate), throwing labor and capital into disarray. Ultimately the transition will be good, but in the meantime, displaced workers will face an unusual amount of lag in finding new work, if only because the industries that were they yesterday have gone and disappeared, requiring extensive levels of retraining.

There are other aspects too, such as the size of government and demographics that look increasingly unfavorable.

Curiously, Jim Grant's admonition to remember history only mentions past slumps in the US. We don't see the word "Japan" mentioned once in the whole article? But unless the laws of economics are different there than they are here, then we can certainly point to examples of bad busts that weren't followed by a quick snap back.