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Dow at 18,000: A buy signal for retail crowd?

Everybody loves a big, round number, especially in the stock market and especially when that number is climbing higher rather than plunging lower.

Investors have endured both over the past seven years, watching as the widely watched Dow Jones Industrial Average climbed past 14,000 then quickly tumbled lower. First 13,000 (November 2007), then 12,000 (June 2008)...then a blazing trail all the down below 7,000 (March 2009) at the height of the financial crisis.

Then the recovery...the leap over 10,000 (November 2009), then past the old highs and onto a succession of new records that has the bluechip index knocking at the door of another milestone.

Though the market's stubbed its toe in recent days, the break of 18,000 seemed almost an afterthought. The market finally reached that mark Tuesday after revised data showed the economy grew at 5 percent in the third quarter, its strongest rate in 11 years.

But now what?

Many market pros, particularly those in the trading pits, dismiss round numbers as something only journalists and novices notice.

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Still, there's something to be said for a big, black headline that indicates the market has crossed another bridge.

"It gives people who have been out of the market since 2009 or have only dabbled around the edges just another reminder that they're missing something," said John Canally, chief economic strategist at LPL Financial. "Each time you get a round number it gets a lot of play in the financial media, and regular water coolers."

That kind of attention can bring at least a short burst of positive momentum.

"It's more psychological than anything else, especially for retail investors," said Jeff Carbone, founder and senior partner for Cornerstone Financial Partners.

Carbone actually is eyeing what he thinks is an even more significant milestone number—5,000 for the Nasdaq. (Of course, the most closely watched indicator among traders, the S&P 500, already has broken through its big milestone—2,000—so its next day in the sun is a ways off.) The Nasdaq, comprised mostly of tech stocks, last traded above that level during the heady days of the dotcom bubble in 2000.

Getting back above 5,000, he said, would be a signal that the market truly has recovered from its bubble-fueled past and ensuing collapse.

Still, he thinks the path beyond will be a little tricky.

"It should be a good year in 2015, but it's going to be more about what you own," Carbone said. "It's not going to be like the last few years when it didn't matter what you owned. It's going to be about being more selective."