When will the end of the world end?

This week opened with an apocalyptic bang, as the Dow Jones Industrial Average hit an intraday low of 7105.94 -- the index's lowest level since Oct. 28, 1997. It rose Tuesday, then fell again Wednesday. In response, pundits everywhere went picking through their tea leaves one shred at a time, looking for the definitive sign that Armageddon is over, so we can all go back to making money again.

What history shows, however, is that the road to recovery from a catastrophic bear market can be distressingly long.

Friday, finance professor Elroy Dimson of London Business School will publish his periodic update of long-term investment returns, which is eagerly awaited each year among the propeller-heads of the investing world. Along with his colleagues Paul Marsh and Mike Staunton, Prof. Dimson compiles vast amounts of reliable data on 17 stock markets around the world all the way back to 1900.

Naturally, the report this year focuses on bear markets. The results shocked even me, and I don't startle easily. Consider this: Prof. Dimson estimates that we'll have to wait nine more years before the Dow average, including dividends, has a 50% chance of hitting its 2007 highs.