Economist and Wharton School of Business professor Jeremy Siegel advises investors to buy more stocks now, especially those that pay dividends and are global in scope.

“It’s exactly times like this, when bearish sentiment has brought down valuations, that your chance of strong returns in the following years is greatest,” Siegel told The New York Times.

“The shocks of the recent past shouldn’t alter investors’ belief in the future.”

Siegel points to the historical fact that when the price-to-earnings ratio is comparatively low, as it is now, positive returns became more probable in subsequent years.

Average real returns would be stellar, Siegel believes, close to 11 percent annually in holding periods from 1 to 20 years.

Siegel says that, over the long run, the market will produce average real returns of more than 6 percent annually, adding that if post-World War II patterns hold in the future the probability of a positive return for the next five years would be 96.6 percent and rise to 100 percent for 10- and 20-year periods.

Thunderstorm Capital’s John Dorfman says that although in practice he uses at least a dozen criteria when picking stocks, price-earnings ratio remains his most important tool.

“It’s important to remember that stocks advance by exceeding expectations,” Dorfman writes in Bloomberg Business Week.

“Low expectations are easier to exceed than high ones, which is why unpopular stocks with low P/E ratios generally do better than popular ones.”