Stocks remain attractive as a long-term investment, though they may plunge as much as 25 percent as the Federal Reserve normalizes its accommodative monetary policy, says John C. "Jack" Bogle, senior chairman and founder of The Vanguard Group.

Investors would do better diversifying their portfolios rather than trying to time the market, he tells CNBC.

The stock markets moves in "fits and starts," and fundamentals such as earnings remain solid, Bogle notes. "What does not move in fits and starts is what the stock market enables you to do, which is own corporate America."

Editor’s Note: 5 Shocking Reasons the Dow Will Hit 60,000

Stock market returns should shadow nominal GNP, which is set to grow approximately 5 percent annually, plus dividends, which should total approximately 2 percent, he maintains.

That gives you a long-term annual return of about 7 percent, which means you would double your money in 10 years, Bogle predicts.

Instead of exiting equities, investors should own some bonds as "ballast" against turmoil in stocks, he suggests.

The Standard & Poor's 500 Index traded at 1,874.57 Tuesday morning.

Many experts anticipate continued gains for stocks.

"The equity market is going to make continued progress in a two-steps-forward, one-step-back kind of progression,” Jim Russell, senior equity strategist for U.S. Bank Wealth Management, tells Bloomberg.

"We're still evaluating how much of the economic weakness is weather related and how much of it is legitimate. We're hopeful that much of the weakness we've seen is weather related and that we'll get a snapback in the second quarter."

Editor’s Note: 5 Shocking Reasons the Dow Will Hit 60,000

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