Peter Lynch ran Fidelity's Magellan Fund from 1977 to 1990 and compounded it at roughly 29% a year (illustrative of the record). It was the best sustained mutual-fund run of its era. Then he wrote One Up on Wall Street (1989) and Beating the Street (1993) to explain how he did it.
Lynch is the patron saint of the intelligent amateur. He claimed that a diligent individual, using what they already see in ordinary life as a source of leads, can beat the professionals. The amateur isn't smarter. They're earlier and more patient, and they're free of the career pressures that make institutions herd.
Lynch's method is a hybrid. He wanted growth, with Fisher's love of expanding businesses, but like Graham he refused to overpay for it. The blend is Growth At a Reasonable Price, or GARP: buy growing companies only when the price is modest relative to that growth. His most-quoted rule of thumb is that the P/E ratio of a fairly priced company will roughly equal its earnings growth rate. A company growing 20% is fairly valued near a P/E of 20. At a P/E of 40 it's expensive, and at 10 it may be a gift. That ratio, P/E divided by growth, is the PEG, and the worked examples compute it properly.
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What does investing in what you know really mean?
"Invest in what you know" is the most misunderstood sentence in investing, and it's universally abused. The lazy reading goes: you like the product, so buy the stock. That's a recipe for disaster, and Lynch spent whole chapters warning against it. His actual claim is narrow and powerful. Your everyday life gives you an early-warning system for trends, and a comprehension edge on businesses you really understand. That edge is a source of ideas to investigate. It's never a substitute for the investigation.
Say you notice the new coffee chain is always packed, or your company has just standardized on a new software vendor, or a regional retailer's parking lot is jammed. You've seen it months before the growth shows up in a broker's model. That observation is a lead. Then you do the work Lynch actually did: read the filings, check the balance sheet, understand the unit economics, confirm the growth is profitable and repeatable, and buy only at a GARP price.
"Know what you own and why you own it" is the other half of the slogan, and the half people forget.
What are Lynch's six categories?
Lynch's most useful teaching tool is his six categories. There's no single kind of "good stock." There are six, and each demands its own question and its own holding period, and a sell trigger of its own. Mislabel the category and you apply the wrong thesis, and you lose. Here they are:
| Category | What it is | The question that decides it | Typical treatment | Sell trigger for this category |
|---|---|---|---|---|
| Slow grower | Large, mature, grows ~GDP (single digits); often high dividend | Is the dividend safe and generous, and why do I own this over a bond? | Own for income, or avoid; little capital upside | Payout cover falls below the level you set, or the dividend-adjusted yield drops under the alternative you would switch to |
| Stalwart | Big, high-quality, grows ~10–12%, recession-resistant | Is the price reasonable (PEG), and has the growth story stayed intact? | Buy on weakness for 30–50% gains, then rotate; a portfolio "anchor" | A stated price-earnings-to-growth ceiling, or a stated percentage gain, whichever arrives first |
| Fast grower | Small/mid, aggressive, grows 20–25%+; the home of ten-baggers and of blow-ups | Is the growth profitable, financed from within, and repeatable (roll-out room)? Is the balance sheet safe? | Lynch's favorite; ride it while the growth and the runway last | Same-store or same-cohort growth below a stated floor for two consecutive periods, or new-unit returns below the hurdle |
| Cyclical | Sales/profits swing with the economy (autos, steel, chemicals, airlines) | Where are we in the cycle, and is the low P/E a peak-earnings trap? | Buy in the trough, sell before the peak; timing dominates | Capacity utilisation above a stated level combined with earnings above your own mid-cycle estimate |
| Turnaround | Beaten-down, troubled, near-death but salvageable | Can it survive (balance sheet), and is the fix real and underway? | Idiosyncratic, uncorrelated with the market; big gains if it works | The justified price-to-book at the completed fix, computed in advance, reached by today's price |
| Asset play | Market cap below the value of hidden assets (real estate, cash, stakes, licenses) | What is the hidden asset really worth, and what catalyst unlocks it? | Needs a local/informational edge on the asset; patience for the catalyst | A stated discount level, plus a date by which the catalyst must have happened |
The category dictates everything downstream. Buy a stalwart and hold it forever, and it underperforms, because you should have rotated after the 40% gain. Sell a fast grower after 40% and you forgo the ten-bagger: you've cut the flower and watered the weed. Buy a cyclical at its lowest P/E, which comes at peak earnings just before the fall, and you've walked into the classic amateur trap. The commodities lesson puts it as a rule: "never value a cyclical on trailing P/E."
So Lynch's habit is to state the category first. It decides whether a low P/E is a bargain or a warning, and whether a 50% gain means sit still or sell.
The trigger column is easy to admire and hard to use, because a trigger written after a stock has moved is just a rationalisation. The special-situations elective turns the six categories into a working drill. You write the trigger as a number on the day you buy, and three of the triggers are computed there instead of described. There's a classification exercise across ten companies, and Lynch's two-minute drill turns a thesis into pre-registered sell criteria. The five legitimate reasons to sell, from the lesson on selling and mistakes, are the general law. These triggers are the specialisation.
What is a ten-bagger?
Lynch coined "ten-bagger," borrowing from baseball, for a stock that returns 10×, and he built his record on a simple observation about them. You don't need many, and their asymmetry forgives a lot of mistakes. A position can only ever fall 100%, and you lose it once. A ten-bagger gains 900%, and you can hold it the whole way up. Take ten equal-weighted positions. One becomes a ten-bagger (+900%), three go to zero (−100% each) and six go nowhere. Your portfolio ends at (10 + 0×3 + 1×6) / 10 = 1.6 times where it started, so you're up 60% despite being flat or worse on nine of ten names. No wonder Lynch's cardinal sin is "pulling the flowers and watering the weeds": selling the winner to feel the gain while averaging down on the losers.
The same arithmetic is the root of the concentration debate at the end of the tour. When a few enormous winners drive everything, the whole game is sizing them well and holding them.
What are the limits of Lynch's retail edge?
Lynch's promise to the individual is real, but it has limits. Knowing where they are is what separates using Lynch from cargo-culting him. Start with the edge. You can spot consumer and workplace trends early. You can be patient in a way a fund manager can't, with no quarterly performance review and no career risk from a two-year drawdown. You can hold small and mid-caps that are too small for big funds to bother with. And nobody forces you to herd into whatever is working this quarter.
Now the limits.
- The edge is for generating ideas and nothing more. The trend you spotted still has to survive the fundamental work, and most consumer favorites are mediocre stocks. A beloved product inside a competitive, low-return, over-valued business is a bad investment.
- Whole sectors give the amateur no edge at all. You have no ground-level insight into a wholesale bank's loan book, a biotech's trial, or a semiconductor fab, and pretending otherwise is how the "invest in what you know" slogan kills people.
- The edge decays as an idea becomes obvious. By the time the packed coffee chain is on a magazine cover, the early edge is priced in.
Lynch also coined "diworseification" for companies that destroy value by buying into businesses they don't understand. Change the subject and the warning fits investors who wander outside their circle of competence just as well.
Worked examples: the six-category sort and the PEG
Worked application (India: the six-category sort). Sort a basket of Indian names by Lynch's taxonomy. The labels are illustrative, and the method is what you're learning.
ITC is a slow-to-moderate grower and a dividend stalwart, a cigarettes-and-FMCG cash machine. The question there is dividend safety and the multiple, and growth heroics don't come into it. A listed QSR chain (a pizza or burger franchisee, say) is a fast grower while the store roll-out runs. Its deciding question is same-store-sales health, plus whether new stores still clear the return hurdle from your unit-economics work. Don't decide it on the trailing P/E. Tata Motors (global autos plus commercial vehicles) is a cyclical. Judge it on the cycle, and never on trailing P/E at the top.
A stressed lender coming out of an asset-quality crisis is a turnaround. Survival is the only question that matters. Here that means capital adequacy and provisioning, as the banks lesson taught. A holding company trading far below the value of its listed stakes is an asset play. India is full of them, and you met the pattern as the holdco discount in the special-situations lesson. It's decided by what the stakes are worth and whether any catalyst (a demerger or buyback) will ever close the discount.
You don't have to agree with every label. Notice instead that each name demands a different analysis, and that choosing the category is the first decision you make.
Worked application (US: the PEG in practice). Take a US stalwart trading at a P/E of 22, growing EPS ~11% with a 2.5% dividend yield. Simple PEG = 22 / 11 = 2.0, expensive on Lynch's scale, where fairly priced is about 1.0. Lynch's dividend-adjusted version credits the yield, since a dividend is part of your return: (growth + yield) / (P/E) = (11 + 2.5) / 22 = 0.61. On his dividend-adjusted scale (>2 attractive, ~1 fair, <1 poor) that also reads poor, which here means expensive. Both flavors agree. It's a quality business at a demanding price.
One caveat keeps you from turning into a PEG robot. The worked examples and the common-mistakes section both hammer it. PEG is a screen. It is not a valuation, because it's blind to how long the growth lasts, the very thing reverse DCF exists to measure. It's also blind to return on capital and to balance-sheet risk. A 25%-grower with a real twenty-year runway and 40% incremental ROIC can rationally trade at a PEG well above 1, because the market is paying for duration. (That's the quality-compounder insight.) Meanwhile a 25%-grower with two good years left is dear at a PEG of 0.5. Use PEG to rank and flag, then value the business properly.