Index-and-Rebalance Investing Rule
Own diversified index funds and rebalance instead of chasing an elusive edge
- Difficulty
- Easy
- Time to result
- ~ongoing to results
- Steps
- 4
- Confidence
- 99%
The index-and-rebalance rule begins by accepting that modern markets contain many intelligent, well-equipped competitors and that any active edge must survive fees, trading costs, and taxes. Instead of repeatedly forecasting winners, the investor selects a diversified allocation of low-cost index funds suited to their goals, horizon, and risk capacity. Contributions follow that allocation, and periodic reviews compare actual weights with the intended targets. When market movement causes material drift, the investor rebalances by directing new money or trading back toward the plan. This converts volatility into a disciplined maintenance action rather than a prompt for emotional prediction. The output is broad market participation, controlled portfolio risk, low implementation costs, and reduced dependence on finding exceptional stocks or managers in advance.
Origin
After leaving Wall Street and studying active-management arithmetic, Henry Blodget adopted indexing and periodic rebalancing as the preferred rule for most investors. Extracted from Masters in Business.
Core principles
- 01Markets contain many skilled and highly competitive participants
- 02Costs and taxes compound the difficulty of active management
- 03Diversification reduces dependence on a few selections
- 04Asset allocation matters more than short-term forecasts
- 05Rebalancing restores the intended risk profile
- 06A simple rule can outperform inconsistent judgment
How to run it
- 1
Set the allocation
Translate goals, time horizon, liquidity needs, and loss tolerance into target weights across diversified asset classes.
Pro tip Choose an allocation you can maintain during a severe market decline.
Watch out Do not select risk solely from recent returns.
- 2
Implement with broad indexes
Use low-cost index funds that provide transparent, diversified exposure to each chosen asset class.
Pro tip Compare total costs, tracking quality, liquidity, and tax efficiency.
Watch out A fund labeled as an index can still be narrow, expensive, or highly concentrated.
- 3
Contribute consistently
Automate investments according to the target allocation. Avoid changing the plan in response to headlines or short-term forecasts.
Pro tip Use new contributions to reduce allocation drift before selling assets.
Watch out Market timing can turn a simple long-term strategy into undisciplined active trading.
- 4
Rebalance periodically
Review the portfolio on a fixed schedule or when allocations cross predetermined bands. Trade only enough to restore the intended risk profile.
Pro tip Consider taxes and transaction costs before rebalancing taxable accounts.
Watch out Excessively frequent rebalancing can create avoidable costs.
In the wild
A saver targets 70% global equities and 30% bonds through low-cost index funds. After a prolonged rally, equities rise to 78%. Rather than predicting an imminent crash, the saver directs contributions to bonds and completes a small annual rebalance back to the target.
→ Portfolio risk returns to the level selected for the saver’s goals without requiring a market forecast.
An institution repeatedly replaces underperforming active managers with recent winners. It adopts diversified index exposure for the portfolio core and limits active allocations to strategies with a clearly documented edge, capacity, and evaluation period.
→ Costs and turnover fall while governance becomes more consistent.
Common mistakes
Using indexing without an allocation plan
Buying an index does not determine how much equity, bond, geographic, or currency risk the investor should hold.
Performance-chasing between indexes
Rapidly switching among sectors or themes recreates active market timing under a passive label.
Rebalancing emotionally
Rebalancing should follow predefined timing or tolerance bands, not fear, excitement, or a market prediction.
Is it for you?
Best for
Most individual investors and institutions seeking diversified, low-maintenance, long-term market exposure.
Not ideal for
It is not designed for investors with a proven, durable edge, specialized liabilities, or a mandate requiring active security selection.
From the transcript
“the smartest thing to do is to hold a portfolio of index funds and rebalance once in a while when the asset allocation.”
“the market is so competitive now and there are so many smart people that to have a consistent edge and to consistently beat all the…”
“your odds of finding those few people who are going to beat the market consistently after taxes and fees are so small that it is…”
From the episode
Business Insider CEO Henry Blodget: Masters in Business (Audio)
Henry Blodget