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The 100 minus age rule is one of the oldest and most widely cited rules of thumb in personal finance. At 30, put 70% of your portfolio in equity. At 50, put 50% in equity. As you age, reduce equity and increase the stable, income-generating portion of your portfolio. Simple, memorable, and, for most people, a reasonable starting point.
I introduced this as part of my allocation framework in Farming Money. Here I want to go deeper, not just explain the rule, but think honestly about when it works, when to deviate, and what the right mental model is for building a portfolio as you age.
Why the rule exists
Equity is volatile. Over a 1-year period, the Nifty 50 has historically delivered anywhere from a 50%+ gain to a 60% loss. Over a 20-year period, those extremes smooth out considerably, and the long-run direction of well-diversified equity has been upward. The logic of the 100 minus age rule is simple: the longer your investment horizon, the more volatility you can absorb, and therefore the more equity you can hold.
When you’re 30, a market crash hurts on paper but you have decades to recover. When you’re 65, a crash just before you need the money is genuinely damaging, you may be forced to sell at depressed prices to fund living expenses, without the time to wait for recovery. Reducing equity as you age is not timidity. It’s rational risk management.
When the rule works well
For a salaried professional in their 30s and 40s with no pension income, a lump-sum financial goal 15–20 years away, and a moderate-to-high risk tolerance, the 100 minus age rule is a good default. It keeps the allocation simple, enforces the right instinct to reduce equity exposure as retirement approaches, and doesn’t require sophisticated forecasting.
The rule is also useful as a rebalancing signal. If your equity allocation has drifted significantly above the target (after a bull run) or below it (after a crash), the rule gives you a reference point for bringing the portfolio back into balance. You don’t have to think about market timing, just rebalance toward the target periodically.
When to hold more equity than the rule suggests
If you have guaranteed income in retirement, a pension from a government job, an annuity, rental income from a property you own free and clear, you have a different risk profile than someone with no floor income. Your living expenses are already covered by that guaranteed income stream. Your investment portfolio is then purely surplus wealth, and you can afford to keep more of it in equity because you don’t need to sell it to fund monthly expenses.
In this situation, someone at 60 with a full pension could reasonably hold 50–60% in equity rather than the 40% the rule would suggest. The pension acts as a bond-like instrument in the portfolio’s overall structure, so you need less fixed income in your financial portfolio to achieve the same risk profile.
India’s demographic trajectory is another reason some people argue for carrying more equity. We’re a young country with a growing middle class and rising corporate earnings over the long run. The long-run equity return potential in India may be higher than in developed markets with aging populations and slower growth. If you believe this, and I broadly do, then staying in equity longer has merit. Some advisors use 110 or 120 minus age instead of 100, acknowledging that longer life expectancy and higher potential returns justify more equity for longer.
When to hold less equity than the rule suggests
If you’re close to a large, non-deferrable goal, your child’s education expenses due in 2 years, a home purchase planned for next year, you should de-risk that specific portion of your portfolio regardless of your age. The 100 minus age rule is about your overall allocation for long-run wealth building, not about money you’ll need in the near term.
The practical approach here is to mentally bucket your money. Money needed in the next 2–3 years: don’t put it in equity at all, use a liquid fund, FD, or short-duration debt fund. Money needed in 3–7 years: some equity, some debt. Money with a 7+ year horizon: the 100 minus age rule applies. If you’ve been running a single pooled portfolio, separating these buckets first will help you apply the rule more sensibly.
If you have low income stability, your income is lumpy, you’re self-employed, or you work in a sector with high job volatility, you need a larger emergency fund and you should be more conservative in your equity allocation than the rule suggests. The rule implicitly assumes reasonably stable income that continues to fund living expenses. If that assumption doesn’t hold for you, skew more conservative.
The rule doesn’t tell you what to do with the non-equity portion
This is where most applications of the rule fall short. The rule tells you how much equity to hold. It doesn’t tell you what to do with the rest. “30% in debt/gold” covers a lot of ground. Short-duration debt funds, long-duration gilts, corporate FDs, PPF, SGBs, gold ETFs, these all behave very differently and serve different purposes.
My approach, which I detailed in Farming Money, is to split the non-equity portion roughly into a debt component (FD, PPF, short-duration debt funds) and a gold component (Gold ETF or sovereign bonds while they were available). Gold provides a different kind of diversification, it often rises when equity falls sharply, and it hedges against inflation and currency risk. Debt provides stability and predictable income. The two serve different purposes within the non-equity allocation.
Implementing the rule practically
Once a year, maybe around your birthday or at the start of the financial year, calculate your actual portfolio allocation. Add up the current market value of all your equity holdings (stocks, equity mutual funds, ETFs). Add up all your fixed income holdings (FDs, PPF, debt funds). Add up gold. Calculate percentages.
If your equity percentage is more than 5–10 percentage points above your target (100 minus your age), sell some equity and move the proceeds to debt or gold to rebalance. If it’s below target (typically after a large market fall), consider increasing equity. This annual check prevents portfolio drift and forces you to buy low and sell high in a systematic way, without having to predict market direction.
Don’t rebalance too frequently. Every trade has a cost, brokerage, exit loads, taxes. Annual rebalancing is usually enough. For most people building wealth over decades, the portfolio doesn’t need constant tweaking. It needs a sound starting allocation and discipline to stick with it through market cycles.
The 100 minus age rule is a starting point, not a destination. Use it as a reference, adjust for your specific situation, and spend more time on the discipline of consistent investing than on optimising the exact percentages. A well-executed 70/30 allocation beats a perfectly optimised 68/32 allocation that falls apart the first time the market drops 30%.
Practical takeaway: Calculate your current equity allocation today. Compare it to 100 minus your age. If it’s off by more than 10 percentage points in either direction, that’s your rebalancing signal for this year, no market prediction needed.
This post is for educational purposes only. It is not financial advice. Mohit Mehra is not a SEBI registered investment advisor. Please consult a qualified financial advisor before making investment decisions.