Rebalancing is not a return lever but a way to steer risk: a fixed rule that sells what has risen and buys what has fallen, and takes the decision out of the moment.
A portfolio drifts on its own. What began as a balanced mix tips out of true as prices move. Rebalancing is the quiet gesture that brings it back.
Rebalancing adds no return. It preserves the decision you once made deliberately.
Rebalancing is often mistaken for a lever that produces more return. It is not. Vanguard puts it precisely in the study “Best Practices for Portfolio Rebalancing” (Vanguard Research, 2010): the primary aim is to keep risk in line with the target allocation, not to maximise return.
The numbers bear this out. For a US 60/40 portfolio over the period 1926 to 2009, Vanguard compared two paths.
| Approach | Return per year | Risk (volatility) |
|---|---|---|
| Rebalanced annually | 8.6 % | 11.9 % |
| Never rebalanced | 9.1 % | 14.4 % |
The portfolio that was never rebalanced earned a marginally higher return, but it drifted to an average equity weight of more than 84 percent and therefore to a markedly higher risk that no longer matched the allocation once chosen. Rebalancing cost roughly half a percentage point of return and at the same time lowered volatility noticeably: a deliberate trade of a little return for a risk that fits your own decision.
This is exactly where it parts ways with timing. A fixed rule, whether by calendar or by threshold, forces you to sell what has risen and buy what has fallen. That is the opposite of performance-chasing, and it takes the decision out of the moment of agitation. You act not because a headline suggests it, but because a rule set in advance requires it.
Once a year is sufficient for most private investors. Alternatively, when positions drift more than 5 percentage points from the target allocation. Rebalancing too often generates unnecessary transaction costs and taxes.
Yes, when you realise gains. Sales in the black are taxable (Abgeltungsteuer, the German flat tax on investment income). Tip: prefer rebalancing through fresh capital (top-up purchases of the underweight position) to avoid taxes.
Calendar: a fixed date (e.g. annually in January). Threshold: only when a position drifts more than X % from the target allocation. Threshold is marginally superior in studies, because it acts only when genuinely needed.
As prices change, the original target allocation in the portfolio shifts. When equities rise and bonds fall, the equity share climbs automatically, and with it the risk. Rebalancing restores the intended distribution.
Rebalancing is not return optimisation, but risk management. It holds your portfolio at the level of risk you deliberately chose.
| Feature | Calendar rebalancing | Threshold rebalancing |
|---|---|---|
| Trigger | A fixed date (e.g. annually) | Drift above X % |
| Effort | Low, predictable | Requires regular monitoring |
| Transactions | Always on the date | Only when genuinely needed |
| Tax burden | Possibly unnecessary sales | Only necessary adjustments |
| In context | A common standard, simple to apply | Reacts more precisely, more monitoring |
Common in practice is a combination of the two: review once a year and act only on larger deviations. A typical tolerance band sits at a few percentage points, around five. That is a widespread convention, not a fixed rule.
Every sale at a gain triggers Abgeltungsteuer (Germany flat tax on investment income). Rebalancing through sales is therefore taxable. Wherever possible you should instead direct fresh capital into the underweight position.
Tax-efficient rebalancing strategies:
Kernaussagen
Hold to the allocation you once chose
Rebalancing is a rule set in advance, not a gut feeling. The Plan-Alignment view shows daily how far your portfolio has drifted from the target allocation you deliberately chose, so the adjustment follows the rule and not the moment.
View Plan-Alignment →