Rebalancing
What is Rebalancing?
Rebalancing is the process of trading a portfolio back toward its target weights after market movements, cash flows, or investment decisions cause those weights to drift.
Why it matters
Without rebalancing, assets that outperform become larger and can quietly change the portfolio's risk profile. Rebalancing restores alignment with the investment policy and creates a disciplined way to sell part of appreciated exposures and add to underweight ones. It can also direct new contributions or withdrawals toward the most useful parts of the portfolio.
Common approaches
Calendar rebalancing occurs on a schedule, such as monthly, quarterly, or annually. Threshold rebalancing occurs when a weight moves beyond a fixed or relative band. A hybrid process reviews regularly but trades only after a threshold is breached. Managers may also use cash flows first to reduce turnover and taxable gains.
Example
A portfolio targets 60% equities and 40% bonds. After an equity rally, weights become 68% and 32%. Rebalancing could sell equities and buy bonds, or direct upcoming deposits into bonds until the gap narrows. The appropriate action depends on permitted bands, tax lots, costs, and whether the target itself remains suitable.
How to evaluate it
Rebalancing should be judged by risk control and adherence to policy, not solely by whether the immediate trade made money. Record the pre-trade weights, target ranges, estimated costs, taxes, and chosen funding source. Over time, compare actual risk with the risk that would have resulted from allowing weights to drift.
Limitations
Trading too frequently can create avoidable costs and taxes, while waiting too long can allow material risk drift. Rebalancing may sell a rising asset before its trend ends, and target weights based on outdated assumptions should not be defended mechanically. The policy should specify review frequency, thresholds, authority, and exceptions.
Practical checklist
Before trading, verify the current target and calculate drift using current look-through values. Use contributions, withdrawals, distributions, and tax-lot selection where they can reduce unnecessary sales. Estimate commissions, spreads, market impact, taxes, and any redemption restrictions. Retain a record of the trigger and resulting weights. Rebalancing rules should be tested across historical periods so their expected turnover and risk control are understood before adoption.
Also known as: portfolio rebalancing