Concept: Mean Reversion
Mean reversion is the tendency for extreme values to return toward the average over time. In markets: abnormally high margins compress, abnormally low valuat...
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What it is
Mean reversion is the tendency for extreme values to return toward the average over time. In markets: abnormally high margins compress, abnormally low valuations recover, and hot sectors cool down while neglected sectors catch up.
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"Mean reversion matlab — jo bahut upar gaya hai woh neeche aayega, jo bahut neeche gaya hai woh upar aayega. Sab cheezein average ki taraf wapas jaati hain."
Why it matters for investing
- High margins attract competition → margins compress toward sector average
- Low valuations reflect pessimism → when conditions improve, valuations re-rate
- Hot sectors become overvalued → future returns disappoint
- Beaten-down sectors recover → contrarian opportunities emerge
- EPS growth rates normalise → 50% growth never sustains; 30% rarely sustains beyond 3-5 years
What mean-reverts and what doesn't
| DOES mean-revert | Does NOT mean-revert |
|---|---|
| Margins for commodity businesses | Revenue of compounders (secular growth) |
| PE ratios of cyclical stocks | Moat widths (can persist or widen) |
| ROCE of businesses without moats | Market share of dominant players |
| Sector allocation performance (rotation) | Technology adoption curves |
| Steel/sugar/cement prices | Index level in growing economy (trends up) |
Key insight: ONLY companies without moats fully mean-revert
Company earns30% ROCE(way above average)
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Does it havea moat?
No moat
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Mean reversion:ROCE falls to 12-15%within 5 years
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PE de-rates accordingly
Wide moat
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ROCE sustained at 25-30%for 10-20 years(NON-mean-reverting)
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Compounding machinePE may stay high
Indian examples of mean reversion
ROCE mean reversion
| Company | 2017 ROCE | 2022 ROCE | Why? |
|---|---|---|---|
| Tata Steel | 5% | 30% | Commodity cycle upswing — will revert downward |
| JSW Steel | 8% | 25% | Same cycle — temporary high |
| Asian Paints | 30% | 28% | Stable — moat prevents reversion |
| TCS | 45% | 42% | Stable — switching costs protect margins |
Valuation mean reversion
| Sector | PE in 2020 (COVID) | PE in 2024 | What happened |
|---|---|---|---|
| Banking | 8× | 15× | Reverted upward as NPA cycle ended |
| IT Services | 18× | 28× | Overshot mean (likely to revert down) |
| Metals | 4× | 12× | Mean-reverted from trough |
| FMCG | 55× | 45× | Slowly reverting from overvaluation |
How to use mean reversion in practice
Strategy 1: Buy at below-mean valuations
- Wait for sectors to trade below their 10-year average PE
- Check that the LOW valuation is due to cyclical factors, NOT permanent business impairment
- Banking at 0.8× book (2020) → reverted to 2× book (2024)
Strategy 2: Be cautious at above-mean margins
- Metals/commodity companies showing "record profits" at cycle peak → margins WILL revert
- Don't pay premium PE for peak earnings
- Tata Steel at 4× PE (2022) = peak earnings × low multiple = actually expensive
Strategy 3: Monitor growth rate normalisation
- A 40% grower at 80 PE will eventually slow to 15-20% growth. PE will also compress.
- The damage: growth halves + PE halves = stock falls 75%
- This is how "quality at any price" investors lose money
Common mistakes
Mistakes to avoid
- Assuming everything mean-reverts — Moat-protected businesses can stay above average for decades (Asian Paints, TCS)
- Ignoring structural changes — Sometimes low margins are the NEW normal (e.g., telecom post-Jio)
- Being too early — Mean reversion takes time. A sector can stay cheap for 3-5 years before recovering
- Confusing value traps with mean reversion — If the business is permanently impaired, it won't revert
- Buying cyclicals at low PE — Low PE on cyclicals means PEAK earnings. Mean reversion here = earnings collapse
Mean reversion timeframes
| What's reverting | Typical timeframe |
|---|---|
| Stock price to fundamental value | 1-3 years |
| Sector valuation rotation | 3-5 years |
| Margins for non-moat businesses | 3-7 years |
| Interest rate cycles | 5-10 years |
| Real estate cycles (India) | 7-12 years |
Related concepts
- Business Cycles — Cyclicality is a form of mean reversion
- Margin of Safety — Buy when prices are below the mean
- Economic Moats — Moats are the only defence against mean reversion of returns