WSJ Interviews Richard Sylla WSJ Amid all the bad news this morning, here's something positive...

Back in 2000, NYU's Richard Sylla predicted a decade of no gains in the stock markets. He was right.

And now he sees the S&P 500 nearly doubling to 2,300 by 2020, reports the WSJ's E.S. Browning.

Sylla also estimates the Dow could hit 20,250 during that same period.

These forecasts are based on market patterns dating all the way back to 1790.

According to Browning's report, "When 10-year-average annual returns [including dividends and adjusted for inflation] dip below 5% and especially when they turn negative, as they did in 2008 and 2009, markets tend to bottom out and begin a recovery, the figures show. Years later, returns top out as investors get overconfident, with average returns above 15%. The market patterns might be related to swings of economic performance and investor confidence."

Sylla warns that the markets could be choppy in the near-term. He also warns that there's a 25% chance gains will fall well short of his forecasts.

Regardless, he believes "2013 to 2022 would be much better."