Here's how many Americans call not investing in the stock market their No. 1 money regret

Suze Orman shares the one thing you should do right now to retire a...

Putting aside money to invest in the stock market can be intimidating, which is, in part, why nearly half of American adults have $0 in stocks, reports Gallup. But if you do it right, it can be the most reliable and effective way to grow your money.

According to Mark Hamrick,'s senior economic analyst, most people think investing in real estate is a better bet but, in fact, it's the stock market that gives the best returns. So it's no wonder, especially in the middle of a bull market, that those who fail to invest often regret it later in life.

In a recent GOBankingRates survey, 11 percent of the 5,000 some American adult participants even called not investing their No. 1 financial regret.

It was the third most popular answer overall and matched the percentage of those who most regretted falling into debt. Meanwhile, 23 percent pointed to "Spending money on non-essentials" and 36 percent said "Not saving enough money."

Older people tend to regret not investing more than younger ones. "Adults ages 65 and older had the highest percentage of respondents choosing this as their top regret — 14 percent — followed by 13 percent of adults ages 55 to 64," GOBankingRates reports.

For younger generations, the percentage was even lower. In fact, more millennials regretted paying for college than not investing in stocks.

The survey also found that men regret not investing more than women. Of male respondents, 15 percent of men chose it as their biggest financial regret, compared to only 9 percent of women, who tended to say their primary regret was not saving enough. Not putting more money away was the top regret for both genders spanning all ages, but 41 percent of women and only 33 percent of men chose the answer.

Investing in the stock market does not have to be difficult. One way you can do it is by having a portion of your paycheck go directly into a tax-advantaged retirement account, such as a , .

If you can automate the process, that's even better. One man did that and was able to retire a millionaire at the age of 37.

It's what David Bach recommends in his book "The Automatic Millionaire." He writes that automating your finances is "the one step that virtually guarantees that you won't fail financially. … You'll never be tempted to skimp on savings because you won't even see the money going directly from your paycheck to your savings accounts."

And because it's such a sure-fire way to build up your savings, you will surely regret it if you don't start taking advantage of the opportunity early.

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Video by Andrea Kramar

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