"Show me an asset class with a better average return. You can't do it! Stocks aren't just the best game in town, they are really the only game in town if your goal is to grow your wealth," Cramer said.
The 10 percent average return on the S&P 500 may not seem impressive at first, despite the fact that it is more than double what one can expect from a 30-year Treasury bond and much more than what a certificate of deposit from a bank pays.
However, if you understand the magic of compounding, the gain is impressive. For instance, if $100 is invested in the S&P 500 and it gains 10 percent in a year, that will generate $110, after another year it's $121 and after a third year it's $133.
The gains will continue to grow, because each year, money is made from the previous year's profits. With that 10 percent average annual return, an investor can double his money in about seven years, Cramer said.
"The magic of compounding works best the younger you are because that means you have more time for your money to grow," Cramer said.
For instance, if a 22-year-old is just entering the workforce, she has more than 40 years before she retires. She can invest $10,000 in an S&P index fund right now with the anticipation that the next 40 years will not be too different from the last 40 years.
In that case, if the average return remains at 10 percent, in 40 years that $10,000 investment will be worth more than $450,000. Making that money did not require any stock picking, trading or even research on individual companies.
"All you have to do after you initially save that money is let it sit on the sidelines, ideally in a 401(k) plan or an IRA so that you don't' have to pay capital gains or dividend taxes on your gains," Cramer said, with reference to Individual Retirement Accounts.
The same logic can be applied to those in different age groups, but the "Mad Money" host insists that it is best to start early to get the biggest bang for your buck.
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