Year-End Portfolio Rebalancing: Impact on Returns vs. Risk

As we close in on the end of the year, it is a good time to take stock of your investment portfolio. If you haven’t already, you should consider rebalancing your portfolio back towards your target asset allocation. Overall, this means selling your recent winners and buying more of your recent losers.

Now, you may think that rebalancing will improve your returns because you are “selling high” and “buying low”. However, the full picture is a bit more nuanced than that. If you think about it, the asset classes with the highest returns should eventually take over the portfolio if you never rebalance. If you started in 1965 with 50% stocks and 50% bonds and did nothing to 50 years, your portfolio in 2015 would have been overwhelmingly stocks. If you kept selling stocks and buying bonds, you would have probably lowered your returns in the long run. So why rebalance?

In his post How Portfolio Rebalancing Usually Reduces Long-Term Returns (But Is Good Risk Management Anyway), Michael Kitces provide a handy visual to summarize the effect of rebalancing into two scenarios:

1. When rebalancing between asset classes with similar returns, the likely effect is to help increase your overall returns while not affecting your risk. An example is rebalancing between US and International stocks.
2. When rebalancing between asset classes with different returns, the likely effect is to help lower your overall risk (improving your risk management in the chart) while decreasing your overall return. An example is rebalancing between stocks and bonds.

In the end, Kitces reminds us while your overall returns probably won’t be enhanced, the net effect of rebalancing is better risk management. I think of it similarly as preventing my portfolio from getting “out of control”. This is why people create “rebalancing bands” that let their portfolios wander a bit but not too much. For example, a 20% target allocation can vary from 15% to 25% before being rebalanced back towards the target number.