In today’s New York Times, Warren Buffett tells us to buy stocks now, while people are scared and times are tough. Wait for the robins, he says, and spring will be over.

He offers a historical illustration to support his advice:

During the Depression, the Dow hit its low, 41, on July 8, 1932. Economic conditions, though, kept deteriorating until Franklin D. Roosevelt took office in March 1933. By that time, the market had already advanced 30 percent. Or think back to the early days of World War II, when things were going badly for the United States in Europe and the Pacific. The market hit bottom in April 1942, well before Allied fortunes turned. Again, in the early 1980s, the time to buy stocks was when inflation raged and the economy was in the tank. In short, bad news is an investor’s best friend. It lets you buy a slice of America’s future at a marked-down price.

No doubt buying on July 8, 1932 would have been opportune. The Dow had fallen for nearly three years, dropping almost 90% off its high of 380 in September, 1929. Today, the Dow has been falling for only a year and is down 40% from its 2007 high. Coincidentally, that’s just the Dow’s position a year after the September 1929 high. Down 40% in the first year. If now is the time to buy, was the historical parallel of now, September, 1930, the time to buy? Not at all. The Dow would go on to lose another 80% in the 22 months after September 1930, not recovering for another 18 years. Not until 1950 would stocks bought in 1930 begin to show a profit.

Buy low, sell high. That’s great advice – for time travelers. Regular folk don’t know whether we’re at the bottom or whether the bottom is far away. Buffett understands the market better than I do, and his recommendation may be sound. But his historical excerpt doesn’t support buying now. Not that any historical excerpt can support any recommendation in the crazy game of chance we call the stock market.