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If at age 26 you invest $20,000 and it earns 4 percent a year, it will grow to $95,000 by the time you reach age 65. If you wait until you're 46 to invest the same amount, it will grow to just $43,000. You've undoubtedly come across examples like this before to prove just how much more a person has to put away to catch up. The obvious advice from our panel to anyone who is behind in her savings is to spend less and save more, but John Claghorn has a further suggestion: "If you are going to be working for another two decades, and you are not going to be withdrawing money from your 401(k) or IRAs to buy a home or pay college tuition, invest as aggressively as you can tolerate."