Rebalancing: what it actually does (and doesn't)
Rebalancing — periodically selling winners to buy laggards back to target weights — is usually sold as a free lunch. The truth is more interesting: it's a trade, and you should know what you're trading.
A clean example
60% Coca-Cola / 40% Microsoft, $10,000, January 2016 to January 2026:
| Buy & hold | Rebalanced yearly | |
|---|---|---|
| End value | $49,968 | $44,167 |
| Volatility | 15.8% | 14.0% |
Rebalancing lowered returns here — because Microsoft kept winning, and every rebalance sold some of the winner to buy more of the laggard. What it bought instead was a steadier portfolio: volatility fell, and the mix never drifted into being a concentrated tech bet wearing a dividend costume.
So when does rebalancing win?
When assets take turns — one zigging while the other zags — rebalancing systematically buys low and sells high and can add return and reduce risk. When one asset trends for a decade, buy-and-hold wins the return contest. Since you can't know in advance which regime is coming, the honest framing is: rebalancing controls risk and keeps your portfolio being the portfolio you chose; any return bonus is situational.