Time it takes: 4 minutes
If you have a diversified portfolio, a run-up in one asset class can throw your mix out of line, increasing risk and eroding returns. An unrebalanced $10,000 portfolio of 80% stocks and 20% bonds would have grown to $21,620 over the past 10 years. If you'd rebalanced annually, you'd have $22,213, or $593 more - and taken less risk to get there. Retooling a 401(k) is easy: With a big plan administrator like Fidelity or Hewitt, rebalancing online takes minutes. In a taxable account, simply direct new money into the lagging fund categories.