It's particularly difficult for people to save during the years when they may be raising a family and paying off a mortgage. But the longer you wait, the more difficult it becomes. That's why it's so essential to start early.

Time is the key.

In our example, four people invest exactly the same amount of money over the same amount of time - $18,000 ($150 a month for 10 years).

Person A doesn't start contributing until he has only 10 years to retirement. Assuming an average 8% return, this person's investments have grown to a total of $27,192.

Person B starts 20 years before retirement and her $18,000 grows to over $58,707.

Person C starts 30 years before retirement and has accumulated a total of $126,743.

Person D starts 40 years before retirement and has accumulated a total of $273,629. And, thanks to the magic of compounding, only $18,000 of the total is money he invested - all the rest is money earning money.

As you can see, Person D earned almost $147,000 more in retirement assets simply by starting 10 years before Person C. So put time on your side and start saving today!