It's the Rodney Dangerfield of bull markets, LPL Financial Chief Market Strategist Jeff Kleintop said Tuesday.
"It gets no respect. This has been the most powerful bull market since World War II," he said. "We've only seen five, six other bull markets that have lasted this long, four years, five months. This is the best of all of them."
On CNBC's "Fast Money," Kleintop likened the stock market rally to a zombie.
"It's unkillable," he said. "I've taken to call it the 'Walking Dead' market, not only because it's unkillable, but it gets no respect."
While inflows into the stock market have been present, Kleintop argued that only about $10 billion has gone into equity mutual funds this year from individual investors.
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"I'm not saying they're still selling as they were in prior years," he said. "They're just not as bullish as I think they probably should be given how much they've been underinvested in recent years." he added.
Why should anyone care, asked Josh Brown of Fusion Analytics.
Kleintop said that underinvestment doesn't necessarily affect prices, "although certainly it would be nice to see the wind to the back of the markets of more buying. But I'm concerned individual investors haven't prepared for their retirement."
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Kleintop said that stocks still appeared buyable at current levels.
"This is a good opportunity," he said. "Looking ahead at the bond market vs. the stock market, this is the time I think individual investors should really consider reallocating back toward equities. I think it will extend but not simply because of the flow of money from the sidelines."