What Are Rebalancing Bands (Deviation-Based)?
'Stocks have risen a bit—should I sell now to trim the weight?' If you turn this worry into a rule, you can decide by a standard rather than by emotion.
What Are Rebalancing Bands?
Rebalancing bands are the rule that 'you rebalance back once the weight drifts beyond a certain range from the target.' Because adjusting every time the market moves a little would increase trading costs and taxes, you set an allowed range (a band) within which 'you leave the drift alone.'
For example, if the target for stocks is 60% and you set a band of ±5%p, you leave it alone when stocks are between 55% and 65%, and return them to 60% once they move outside that range.
Swedroe's 5/25 Rule
The 5/25 rule organized by Larry Swedroe is widely known.
① For an asset with a target weight of 20% or more: rebalance if it drifts by ±5%p in absolute terms. (e.g., target 60% → when it reaches 55% or 65%.)
② For an asset with a target weight below 20%: rebalance if it drifts by 25% of the target in relative terms. (e.g., target 15% → 25% of 15% is ±3.75%p, i.e., when it reaches 11.25% or 18.75%.)
The distinctive feature is handling large weights by absolute range and small weights by relative range.
5/25 is not an absolute correct answer but a widely used example rule. You can adjust the band width to fit your own trading costs, taxes, and psychology.
What Vanguard's Research Says
Vanguard's rebalancing research leans toward 'no method makes a big difference.'
It concluded that using a reasonable checking interval (about once a year) and a reasonable drift threshold (around 5%) provides sufficient risk management for most diversified portfolios. The performance differences among monthly, quarterly, and annual rebalancing were not large.
In other words, rather than hunting for the 'perfect band,' it is more important to set a rule and stick to it consistently.
常见问题
Q. Is it better to set the band narrower?
The narrower the band, the more precisely you hold the target weight, but the number of trades, costs, and taxes increase. According to Vanguard's research, around 5% is enough for most cases, and the extra benefit of an overly narrow band was not large.
Q. Do rebalancing bands boost returns?
The main purpose is not to maximize returns but to manage risk (weight concentration). Because you sell what has risen and buy what has fallen, it tends to lower volatility, but in a strong bull market it may actually give up some of your returns.
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📋 结果基于历史数据计算,过去的收益不代表未来的收益。
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