When (and If) to Rebalance After a Bull Run

Key Factors to Consider Before Rebalancing

After a strong market rally, many investors face the same question: Should I rebalance my portfolio now or keep riding the upswing?

The answer is not simple. And more importantly, rebalancing is not always the best immediate decision.

To help you evaluate and make the best choice, here’s a complete explanation with professional insights.

What happens to a portfolio after a bull run?

During a bull market, higher-risk assets (mainly equities) tend to outperform other classes, such as bonds or cash equivalents.

This creates a phenomenon known as portfolio drift.

Practical example:

Asset Initial Allocation After Rally Stocks 60% 75% Bonds 30% 20% Cash 10% 5%

Even without doing anything, your portfolio becomes riskier.

You didn’t change your strategy—the market changed it for you.

Why rebalance?

Rebalancing helps restore the original allocation, control risk levels, realize gains, and avoid excessive concentration.

In practice, it’s the classic move: Sell part of what went up and buy what lagged behind.

But be careful: rebalancing too early can be costly.

A common mistake among U.S. investors is automatically rebalancing after any significant gain.

This can cut long-term returns, reduce exposure to strong trends, and increase costs from fees and taxes.

Real case: post-2020 tech rally

After the rally in big tech (Apple, Microsoft, Nvidia), many investors reduced exposure too early.

Result: they missed a significant portion of the continued rally and became underallocated in winning sectors.

When does it make sense to rebalance?

Here are 3 main triggers:

1. Significant allocation drift (threshold-based)

A common rule in the U.S. market is the 5% rule.

If an asset deviates more than 5 percentage points from its original allocation, rebalancing may be considered.

Example:

• target: 60% stocks
• current: 68%

👉 possible rebalance

2. Change in risk profile

If your situation changes—such as with approaching retirement or income changes—it may make sense to reduce risk, regardless of the market.

3. Relevant macroeconomic events

Environments such as Fed rate hikes, looming recession, or persistent inflation may justify strategic adjustments.

When NOT to rebalance?

Not every rally requires action. Situations where it may make sense to stay put:

• Long-term horizon (10+ years)
• Gains supported by strong fundamentals
• Low liquidity needs

In many cases, doing nothing is an active decision.

Rebalancing strategies

1. Calendar-based (time-based)

• Quarterly
• Semiannual
• Annual

✔ Simple
❌ Ignores market conditions

2. Threshold-based (deviation-based)

• Based on percentage drift

✔ More efficient
✔ Responsive to market

3. Hybrid approach

Combines time + deviation

👉 Considered the most robust

Comparison table:

Strategy	Advantage	Disadvantage
Calendar	Simplicity	May be inefficient
Threshold	Precision	Requires monitoring
Hybrid	Balance	More complex

Tax impact (critical in the U.S.)

Example:

• Sell before 1 year → higher tax
• Sell after 1 year → lower tax

👉 This directly affects decision-making.

Smart alternative: rebalance with new contributions

Instead of selling assets, many investors choose to:

👉 Direct new contributions into underweighted asset classes.

Example: portfolio overweight in stocks New investments go into bonds.

This approach avoids taxes and maintains strategy.

Case example: ETF investor in the U.S.

John invests in:

• VOO (S&P 500)
• BND (bonds)

After a bull run: Stocks went from 60% to 72%.

Instead of selling, he directed new contributions to BND. Result: gradual rebalancing without triggering tax events.

Risk of overtrading

Rebalancing too frequently can lead to higher costs, emotional decisions, and reduced efficiency.

The role of diversification

After a rally, many portfolios become concentrated in tech and large caps.

Rebalancing can help redistribute risk and include small caps, international assets, or bonds.

Practical decision framework

Before rebalancing, ask yourself:

• Has my portfolio significantly drifted?
• Has my risk profile changed?
• Are there relevant tax implications?
• Is the market in a sustainable trend?

If most answers are “yes,” → consider rebalancing. If not, it may be better to hold.

The balance between discipline and flexibility

Investing is not about reacting to every market move.

It’s about having a plan, following clear rules, and avoiding emotional decisions.

Rebalancing is a tool—not an obligation.

Conclusion

After a bull run, the urge to act is strong. But acting is not always the best move.

For U.S. investors, rebalancing should be guided by strategy, data, and tax context—not fear or euphoria.

Because in the end:

👉 The best investor is not the one who reacts fastest—but the one who decides best.

Written by

Gabriel Gonçalves