Monday, April 13, 2009

How Often Should You Rebalance Your Portfolio?

It is often suggested that you should rebalance your portfolio every year. But you might ask yourself, "why every year"?

I think it makes sense to think about why you rebalance and what is happening to your portfolio when you do or do not rebalance. I believe that the top 2 reasons for rebalancing are:
  • Control the risk profile of your portfolio
  • Capture reasonable gains when they occur (buy low, and/or sell high)
How does rebalancing on a timed schedule (quarterly, yearly, etc) help with either of these goals? For example in a volatile market, with wild swings up and down in short time frames, we optimally want to rebalance frequently at market tops and bottoms. This would achieve both goals. In a stagnant market, we might not need to rebalance for many years. This would also achieve both goals.

However, if we agree that we cannot time the market, then we have no way of knowing where those tops and bottoms are, so most of us need some rules of thumb so that we don't forget to rebalance altogether (or rebalance too often--think about transaction costs and taxes on capital gains).

The rule of thumb that is easiest to remember is a timed schedule. This is also probably why it is the most frequently suggested rebalancing strategy. Maybe it's on your birthday, or after you receive your notice of assessment from the CRA. If you will forget to rebalance without a timed schedule, it makes sense to use calendar dates for rebalancing, whether you decide it is every quarter, every year, every 2 years, or whatever is convenient for you. The once-a-year suggestion appears to be historically sound and also keeps transaction costs within reason.

If you have more discipline and follow your portfolio more closely, a more direct approach to achieving the goals of rebalancing is to set limits on how much an asset is allowed to deviate from your target allocation. For instance if you have a 60/40 portfolio and you decide that a 10% deviation is when you are out of your comfort zone, you would rebalance if your portfolio became 70/30 or 50/50. The number you choose as your deviation limit depends on your risk tolerance and what you think are fair gains to cash out on. Using this method, you would be rebalancing whenever it is necessary according to your rules for achieving the rebalancing goals.

While I think that the timed schedule is a fine rebalancing strategy, it does seem to me to be an indirect way to achieving the ultimate goals of rebalancing. If you have the discipline and energy, setting deviation limits is probably a more direct approach.

1 comment:

  1. I'm glad this post could help you come up with a plan that makes sense for you. The actual ranges that you choose are personal, and I chose 10% in my post only as an example.

    If you're making a conscious decision to use a wider range now because you feel that the current economic situation is unique, it might be a good idea to also make a plan for when you will switch back to a range that is more within your comfort zone. For instance, maybe it's when you see the VIX volatility index hit a certain number that you squeeze your range back down.

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