(Fortune Magazine) -- Is it time to buy U.S. stocks?

According to both this 85-year chart and famed investor Warren Buffett, it just might be. The point of the chart is that there should be a rational relationship between the total market value of U.S. stocks and the output of the U.S. economy - its GNP.

Fortune first ran a version of this chart in late 2001 (see "Warren Buffett on the stock market"). Stocks had by that time retreated sharply from the manic levels of the Internet bubble. But they were still very high, with stock values at 133% of GNP. That level certainly did not suggest to Buffett that it was time to buy stocks.

But he visualized a moment when purchases might make sense, saying, "If the percentage relationship falls to the 70% to 80% area, buying stocks is likely to work very well for you."

Well, that's where stocks were in late January, when the ratio was 75%. Nothing about that reversion to sanity surprises Buffett, who told Fortune that the shift in the ratio reminds him of investor Ben Graham's statement about the stock market: "In the short run it's a voting machine, but in the long run it's a weighing machine."

Not just liking the chart's message in theory, Buffett also put himself on record in an Oct. 17 New York Times op-ed piece, saying that he was personally buying U.S. stocks after a long period of owning nothing (outside of Berkshire Hathaway (BRKB) stock) but U.S. government bonds.

He said that if prices kept falling, he expected to soon have 100% of his net worth in U.S. equities. Prices did keep falling - the Dow Jones industrials have dropped by about 10% since Oct. 17 - so presumably Buffett kept buying. Alas for all curious investors, he isn't saying what he bought.



