KARACHI: Every investor eventually faces the same uncomfortable comparison. One share trades at twelve times its earnings and grows at five per cent a year. Another trades at thirty times earnings and grows at twenty-five per cent. Which is expensive? The price-to-earnings ratio alone cannot answer, because it prices the present and ignores the trajectory. The PEG ratio — price-to-earnings divided by growth — exists to force that missing dimension into the comparison. Popularised by the American fund manager Peter Lynch, who used it to hunt for growth he had not overpaid for, PEG is crude, assumption-hungry and easy to misuse. It is also, handled with respect, one of the fastest sanity checks in a growth investor's toolkit.
The formula and the famous rule of thumb
The calculation has three ingredients. Start with the P/E ratio — share price divided by earnings per share, usually the forward or trailing figure depending on your data source. Then take the expected annual growth rate of earnings per share, expressed as a whole number: growth of 15 per cent a year enters the formula as 15, not 0.15. Divide: PEG = P/E ÷ EPS growth rate. Lynch's rule of thumb held that a fairly priced growth company has a PEG around 1 — the multiple you pay roughly matches the growth you get. Below 1, the growth looks cheap relative to its price; above 2, you are paying a princely sum for growth that had better be spectacular and durable. The rule's appeal is its symmetry: it says a P/E of 30 is no sin for a business compounding at 30 per cent, and a P/E of 8 is no bargain for a business shrinking at 2 per cent — assertions the naked P/E would never make. Like all rules of thumb, it marks the start of an investigation, and our guide to valuing a PSX stock places it among its sibling multiples.
A worked example with invented numbers
Consider two fictional companies, both invented for illustration. Swat Software Limited trades at Rs 240 per share with earnings per share of Rs 12, so its P/E is 20. Analysts expect its EPS to grow at 20 per cent a year over the next few years. Its PEG is 20 ÷ 20 = 1.0 — squarely on Lynch's fair-price line. Its fictional peer, Malir Foods Limited, trades at Rs 150 with EPS of Rs 12.50 — a P/E of just 12 — but its earnings are growing at only 6 per cent a year, so its PEG is 12 ÷ 6 = 2.0. By P/E, Malir looks the bargain; by PEG, Swat's growth is the better purchase and Malir's cheapness is fully explained by its plodding trajectory. Now stress the example, because the stress is the lesson. Suppose Swat's growth slows to 12 per cent: its PEG rises to 20 ÷ 12 ≈ 1.7 and the case collapses — at the same price. Nothing about the company changed except an expectation, which is precisely PEG's weakness: the denominator is a forecast, and forecasts are where optimism goes to be expressed in numbers. A PEG quoted without asking whose growth estimate, over which years, off what base, is a number with its scaffolding hidden.
Which growth? The denominator's many disguises
Growth can be measured backwards — the compound rate of the last three or five years, a fact, but possibly a stale one if the company has just changed gear — or forwards, from analyst forecasts, which embed tomorrow's hopes and herd behaviour. It can be measured over one year, which makes it hostage to base effects: earnings rebounding from a depressed year can post a meaningless 80 per cent growth rate that annualises into a nonsense PEG near zero. Cyclical companies defeat the measure entirely at turning points, since earnings at a cycle's peak or trough are unrepresentative of any trend. Seasoned users therefore prefer a normalised, multi-year expected growth rate — three to five years is the common window — and sanity-check it against the company's actual reinvestment economics: a business can only compound earnings as fast as its return on capital and reinvestment rate allow, a constraint our DuPont analysis guide makes visible by connecting growth to ROE and retention. If a quoted growth rate implies the company will, within a decade, be larger than its entire industry, the PEG built on it is fiction squared.
There is also a quieter choice buried in the denominator: growth of earnings per share is not the same as growth of earnings. A company can raise EPS growth above its profit growth by shrinking the share count through buybacks, or depress it by issuing shares for acquisitions — financial engineering that changes the per-share trajectory without changing the underlying business trajectory by a rupee. Since the shareholder experiences returns per share, EPS growth is arguably the right input; but the analyst should know which engine produced it, because buyback-driven growth exhausts itself when the cash or the cheap shares run out, while operating growth compounds as long as the market and the reinvestment opportunities last. A PEG that looks identical for both companies conceals that difference in durability completely.
PEG across the growth–value divide
The ratio's natural habitat is the middle ground of investing — neither deep value nor hyper-growth, but what Lynch called "growth at a reasonable price," the philosophy our guide to growth versus value on the PSX contrasts with its neighbours. Used comparatively within a sector, PEG can surface genuine anomalies: two pharmaceutical firms with similar prospects where the market charges one twice the other's growth-adjusted price. Used absolutely, across sectors and countries, it deceives: a utility can essentially never post the growth that would bring its PEG near 1, and a young platform company may deserve a heroic PEG if its runway is long — though "deserve" is doing heavy lifting in that sentence, since the history of growth investing is littered with companies whose forecast growth was real but whose shares still fell, because the price had capitalised even more growth than arrived. That last point deserves emphasis: PEG compares price with expected growth, but markets price expectations too. A PEG of 0.8 may not mean the market has overlooked the growth; it may mean the market disbelieves it, or believes it but prices the risk of its failure, the debt on the balance sheet, or the controlling shareholder's record. The ratio cannot adjudicate that argument. It can only pose it crisply.
Adjustments and refinements
Practitioners have patched PEG's obvious holes in several ways. The dividend-adjusted version adds the dividend yield to the growth rate in the denominator — (P/E) ÷ (growth + yield) — recognising that a shareholder's total return comes from payouts as well as expansion; it flatters mature payers relative to the plain version and is sometimes called the PEGY ratio. Others replace forecast growth with a conservative blend of historical and expected rates, or cap the growth input at some ceiling — 25 or 30 per cent — on the argument that no company sustains more and that uncapped denominators let any price be justified. A complementary discipline is to lay PEG beside the multiple history of the company itself: a stock whose PEG has doubled because its price ran ahead of unchanged forecasts is telling a simpler story than any formula. And for companies whose earnings are negative or trivially small, PEG is simply inapplicable — there is no meaningful multiple and no stable growth rate, and valuation must fall back on sales multiples, asset values or the cash-flow methods covered by our free cash flow guide.
Using PEG on the PSX without fooling yourself
Pakistani conditions sharpen every caveat. Earnings forecasts for smaller PSX companies are sparse and often stale, so a computed PEG may rest on a single broker's spreadsheet. High and variable inflation and policy rates push nominal growth rates up across the whole market — a 15 per cent nominal EPS growth in a year of double-digit inflation is a different achievement from the same number in a low-inflation economy, and PEG comparisons imported from low-inflation markets mislead accordingly. Currency effects flatter exporters' rupee earnings in depreciation years and reverse later. Thin trading means the P/E numerator itself can rest on a stale price. None of this bans the tool; it instructs its handling. Compute PEG from growth you have interrogated yourself, demand a discount — a PEG visibly below 1, not at it — before calling growth cheap, and treat the exercise as one witness among several, cross-examined by the statements. A ratio whose entire purpose is to stop you overpaying for a story should never become a story you overpay for.
Re-rating and de-rating: watching PEG move
Because PEG has a price in its numerator and an expectation in its denominator, it changes for two entirely different reasons, and the profitable habit is knowing which one just moved. When a company's prospects genuinely improve — a capacity expansion announced, a market entered, margins inflecting — expected growth rises and, until the price catches up, PEG falls: the market is offering more future per rupee. When the price alone races ahead on enthusiasm, with forecasts unchanged, PEG rises: the same future now costs more. Investors call the first dynamic the early stage of a re-rating and the second the late stage of one, and confusing them is expensive, because a stock whose PEG has doubled on price alone has not become a better business — it has become a more demanding one. The mirror image, de-rating, is where PEG earns its keep as a shopping instrument: a sound grower whose price has fallen with a sector-wide panic, or on a single disappointing quarter that does not impair its multi-year trajectory, presents a PEG compressed by mood rather than by arithmetic. Lynch's own practice leaned heavily on exactly this situation — solid growth temporarily priced as if it had already ended — combined with a balance sheet strong enough to guarantee the company would survive to deliver the growth the ratio was counting.
A miniature comparison shows the discipline assembled. Imagine two fictional exporters after a currency shock: the first's rupee earnings have leapt, its trailing growth looks enormous, and its PEG on trailing numbers appears tiny — but the growth is a translation effect that will not repeat, so the forward PEG on normalised earnings is the honest figure and it is unremarkable. The second exporter shows dreary trailing growth because it spent two years building a plant that has just commissioned; its forward growth, off real new capacity, is strong and its forward PEG is genuinely low. PEG used naively buys the first and ignores the second; PEG used with the interrogation habits this guide has described — whose growth, over which years, off what base, earned how — reaches the opposite conclusion. The ratio is a lens, and like every lens it rewards the user who knows what it distorts.
To close, a note on temperament. PEG flatters decisive temperaments because it seems to convert judgement into arithmetic, but Lynch himself paired it with homework the ratio cannot do — knowing why the company grows, who its customers are, and what could stop it. The investors who get hurt by PEG are rarely hurt by the division; they are hurt by treating the output as permission to stop asking questions at exactly the moment the questions mattered most. Let the ratio do its one job — flagging where price and growth look out of line with each other — and then go and find out, from the statements and the business, which of the two is wrong.
This article is educational content explaining a popular valuation heuristic; it is not financial advice, and the companies and figures in its examples are fictional illustrations, not market data.
Key takeaway: PEG divides the P/E by the earnings growth rate so that price is judged against trajectory — around 1 is Lynch's fair-price line — but the whole ratio stands or falls on the quality of a growth forecast nobody can guarantee.
