Equity Research puzzles, solved step by step
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059A company is growing its after-tax operating profit at 20% a year and earns a 15% return on every rupee of new capital it invests. What share of its profit must it reinvest to keep growing at 20%, and what does that do to its free cash flow?Buy-side equity researchLong-only asset management
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What share of profit must the company reinvest?
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It must reinvest about 133% of its profit, so free cash flow is negative. Growth equals the reinvestment rate times the return on invested capital, so the reinvestment rate is 20% divided by 15%, or 1.33. On Rs 100 crore of after-tax operating profit the company must invest Rs 133 crore, leaving free cash flow of minus Rs 33 crore, which has to come from lenders or shareholders.
Where does the rule that growth equals reinvestment times return come from?
A tailor earns Rs 15 a year for every Rs 100 of sewing machines she owns. To earn 20% more next year she needs 20% more machines, and buying them takes cash. Profit grows only as fast as the capital that produces it, so growth equals the share of profit reinvested times the return that capital earns. Turn it round and the reinvestment rate is growth divided by the return on invested capitalAfter-tax operating profit divided by the capital tied up in the business, fixed assets plus working capital.: 20% over 15% is 133%.
The relationshipg growth in after-tax operating profit RR reinvestment rate, the share of profit invested back in the business ROIC return earned on each rupee of new capital What it says in wordsThe share of profit a company must reinvest is its growth rate divided by the return it earns on new capital.To grow 20% at a 15% return on capital the company must reinvest Rs 133 crore against Rs 100 crore of profit, a bar a third taller, leaving free cash flow of minus Rs 33 crore that must be funded from outside. Does negative free cash flow mean the business is bad?
Not on its own. The check on the right of the figure proves the arithmetic: Rs 100 crore of profit on Rs 667 crore of capital is 15%; add Rs 133 crore and capital is Rs 800 crore, which earns Rs 120 crore next year, exactly 20% more. Negative free cash flow from growth creates value as long as the return on new capital beats the cost of that capital, and destroys value when it does not. The questions an analyst asks are how long the gap can be funded, and at what price.
Return on new capital Reinvestment to grow 20% Free cash flow on Rs 100 crore profit 10% 200% of profit Rs -100 crore 15% 133% of profit Rs -33 crore 20% 100% of profit Rs 0 crore 30% 67% of profit Rs 33 crore 40% 50% of profit Rs 50 crore At a fixed 20% growth rate, a higher return on capital means less reinvestment and more free cash flow; at a 20% return the company exactly funds itself. What does this tell you about a growth story pitched in an interview?
That growth is never free, and its cost depends on returns. Two companies growing 20% can have opposite cash profiles: one earning 40% on new capital throws off half its profit, one earning 10% needs twice its profit again every year. When someone pitches a fast grower, ask for its return on new capital before you ask for its growth rate.
Where candidates lose it
Candidates reach for a reinvestment rate below 100% out of habit, because it feels impossible to invest more than you earn. It is not impossible; it only means raising money every year, and that is exactly what the interviewer wants you to notice.
The second slip is concluding the business is bad. A 15% return on new capital is healthy against most costs of capital. Say that the value of growth depends on that return beating the cost of capital, and that the funding need, not the growth, is the risk.
What the interviewer asks next
- What growth rate can the company sustain while funding itself entirely from profit?
- If return on new capital falls to 8% and the cost of capital is 11%, is growth adding value?
- How would you spot, in the cash flow statement, a company growing faster than its returns can fund?
061A company grew EPS 40% last year while its sector grew 10%. Assume that 30% of any company's growth above the sector average persists into the following year, a persistence coefficient of 0.3. What EPS growth should you forecast for next year?Sell-side equity researchBuy-side equity research
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What growth do you forecast for next year?
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About 19%. Start from the sector's 10%, the base rate, and keep only the part of the outperformance that tends to persist. The excess was 40% - 10% = 30 points, and a coefficient of 0.3 keeps 9 of them, so the forecast is 10% + 0.3 x 30 = 19%. Extreme results are partly luck, and luck does not repeat, so the forecast sits much nearer the average than last year's number.
Why not forecast 40% again?
A student who scores 95 in one mock exam, when the class averages 60, is probably both able and lucky that day. On the next mock she is likely to beat the class again, but by less, because the luck part does not come back. An extreme result is part skill and part luck, and only the skill carries forward, so the best forecast pulls the result back towards the average. The persistence coefficient says how much pulling to do: 0.3 means 30% of the gap survives and 70% fades.
At 40% growth last year, extrapolating gives 40% and assuming nothing persists gives the sector's 10%, while keeping 30% of the 30 point excess gives a forecast of 19%, much nearer the average than the outlier. The relationship\hat g next year's forecast growth \bar g the sector average, the base rate g the company's growth last year \beta the persistence coefficient, the share of the excess that carries over What it says in wordsThe forecast is the average plus the share of last year's excess that tends to persist.Where does the 0.3 come from, and what if you are not given it?
It is an empirical fact about a set of companies, not a law. You would estimate it by comparing one year's growth with the next across many companies in your universe over several years. Without data, the question to ask is how much of last year's jump came from something that recurs, such as a new plant or share won from rivals, and how much from something that does not, such as a one-off order, a weak base year or a tax credit. A jump built on recurring drivers deserves a higher coefficient.
How does this show up on a research desk?
Forecasts for last year's winners are often extrapolations with a haircut too small. A stock priced as if 40% growth continues is exposed when growth drifts back towards the sector, even if the company stays better than average. Say that link after the number: it shows you understand why the interviewer framed the question around a forecast rather than a fact.
Where candidates lose it
Candidates either extrapolate 40% or, overcorrecting, snap all the way back to the sector's 10%. Both ignore the coefficient they were handed, which is the entire point of the question.
The quieter slip is multiplying the whole 40% by 0.3 and saying 12%. The shrinkage applies to the excess over the average, not to growth itself. Anchor on 10%, then add back 30% of the 30 point gap.
What the interviewer asks next
- What would a coefficient of 1, or of 0, say about the business?
- Why might growth that came from winning market share persist more than growth from a one-off order?
- How would you estimate the coefficient from ten years of data?
076A forensic accounting screen catches 90% of the companies that are manipulating their earnings and wrongly flags 4% of the clean ones. If 2% of listed companies manipulate, what share of the companies it flags are actually manipulating?Sell-side equity researchBuy-side equity research
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Before you calculate: the screen catches 90% of manipulators. Roughly what share of its flags are real?
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About 31%: roughly two flags in three are false alarms. Take 10,000 companies. 200 manipulate and the screen catches 180 of them. 9,800 are clean and 4% of them, 392, are flagged anyway. Of 572 flags, 180 are real, which is 31.5%. The false alarms come from the huge clean group, so a rare problem plus a small error rate swamps the true hits.
Why is the answer not 90%?
Think of the smoke alarm in a kitchen. It goes off for every real fire, and it also goes off for burnt toast. Fires are rare and toast burns every week, so most of the times the alarm sounds, nothing is on fire. The 90% tells you how the screen treats a manipulator; the question asks how often a flag is right, and that depends on how many clean companies are standing there to be wrongly flagged. Those are two different conditional probabilities, and swapping them is the whole trap.
Of 10,000 companies, 200 manipulate and the screen flags 180 of them, while 392 of the 9,800 clean companies are flagged by mistake, so only 180 of 572 flags, 31.5%, point at a real manipulator. How do you set it up so the arithmetic is easy out loud?
Pick a round population and count people, not probabilities. With 10,000 companies the 2% who manipulate are 200, and 90% of them, 180, get flagged. The clean 9,800 produce 4% false flags, 392. Once the tree is drawn, the answer is just flagged guilty over all flagged: 180 over 572. This counting method is called natural frequenciesStating a probability problem as counts out of a round population, such as 180 out of 10,000, instead of as percentages. It makes conditional reasoning much easier to follow., and it is far harder to get wrong than juggling Bayes' formula in your head.
The relationshipP(M | F) the chance a flagged company is manipulating 0.02 the share of companies that manipulate, before any screen 0.90 the share of manipulators the screen catches 0.04 the share of clean companies it flags by mistake What it says in wordsTrue flags divided by all flags, where all flags include the mistakes made on the large clean group.What does this mean for how an analyst uses a screen?
A flag is evidence, not a verdict. It moves the odds from 2 in 98 to 180 in 392, a jump of 22.5 times, which is exactly 90% divided by 4%. That is why a flag should start a deeper read of the notes to the accounts, never end one. If a second, independent check with the same accuracy also flags the company, the odds multiply again and the chance rises to about 91%. The limitation is the word independent: two ratio screens built on the same receivables line will fail together.
Where candidates lose it
Candidates answer 90%, or subtract to get 86%, because the question hands them one big accurate-sounding number and they carry it straight to the answer. The interviewer is checking whether you ask how common the thing is before trusting the test.
The second loss is getting 31% and not saying what it means. Close with the working point: a flag is where the forensic work starts, and a short thesis resting on one screen alone is two parts false alarm to one part signal.
What the interviewer asks next
- If manipulation were 10% of companies, what share of flags would be real?
- How low must the false flag rate go for half of all flags to be real?
- Why might two forensic screens not be independent of each other?
078Size the Indian decorative paint market in Rs crore a year, from the housing stock up, and then check your answer from the top down.Indian brokerage researchSell-side equity research
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Which single assumption moves the bottom-up answer most?
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About Rs 50,000 crore a year on these assumptions, with the two routes landing within 5% of each other. Bottom up, urban repaints give Rs 35,000 crore, rural repaints Rs 9,000 crore and new homes Rs 7,200 crore, Rs 51,200 crore in all. Top down, 140 crore people spending Rs 350 a head gives Rs 49,000 crore. Every input is an assumption to be checked against published data.
Where do you start the bottom-up build?
Start from what gets painted, not from who sells paint. A home is repainted every few years, and each repaint uses a number of litres set by the wall area. So the market is homes, divided by the repaint cycle, times litres per job, times the price of a litre, plus the new homes painted for the first time. Split urban and rural before you multiply anything, because they differ on every input: bigger walls, shorter cycles and costlier emulsions in cities; smaller homes, longer cycles and cheaper finishes in villages.
State each number as an assumption and move on. Assume 140 crore people in about 30 crore households, a third urban. Urban homes are repainted every five years, with 3,000 square feet of wall and ceiling; rural homes every eight years, with 1,200 square feet. A litre covers about 60 square feet for a two-coat finish, and a litre costs a blended Rs 350 in cities and Rs 180 in villages. About 60 lakh new homes a year take 40 litres each at Rs 300. None of these is a published figure; each is a round number you can defend in one sentence and replace later. Confirm household counts against the latest census or survey data.
Segment Jobs a year, crore Litres per job Rs per litre Market, Rs crore Urban repaints 2.00 50 350 35,000 Rural repaints 2.50 20 180 9,000 New homes 0.60 40 300 7,200 Bottom up total 51,200 On these assumptions urban repaints are Rs 35,000 crore, rural repaints Rs 9,000 crore and new homes Rs 7,200 crore, a bottom-up market of Rs 51,200 crore a year. How does a top-down check work, and why does it help?
Go the other way with a number you can feel. A family of four that repaints a flat for about Rs 7,000 of paint every five years spends Rs 1,400 a year, which is Rs 350 a head. Across 140 crore people that is Rs 49,000 crore. Two routes built from different inputs that land within a few percent of each other are worth more than one route worked to the last rupee. If they had landed a factor of two apart, you would know one assumption was wrong and go looking for it.
The bottom-up build from homes reaches Rs 51,200 crore and the top-down build from spend per head reaches Rs 49,000 crore, so two independent routes agree on a market of about Rs 50,000 crore a year. Then name your weakest input. Urban repaints are about 68% of the answer, so the urban cycle carries the most risk: at six years instead of five, the urban figure falls to Rs 29,167 crore. An analyst would close by saying which number to check first, and where: the decorative revenue that listed paint makers publish in their annual reports is the natural cross-check.
Where candidates lose it
Candidates start from the paint companies, guessing their sales and adding them up, which is not an estimate but a memory test. Others multiply the whole population by one litre figure and never split urban from rural, so every average they use is wrong for most of the homes it touches.
The second loss is stopping at one number. Without a top-down check and a named weakest assumption, the interviewer cannot tell whether your Rs 50,000 crore is reasoning or luck.
What the interviewer asks next
- How would the answer change if half of rural homes used lime wash instead of paint?
- Which part of this market grows fastest, and why?
- How would you split the market between economy and premium paint?
- What share of the market goes on exterior walls, and how would you estimate it?
079A stock's price compounds at 8% a year for ten years, and it pays a 3% dividend yield that you reinvest. What does Rs 1 lakh become on price alone, and what does it become on total return?Long-only asset managementBuy-side equity research
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Price alone takes Rs 1 lakh to about Rs 2.16 lakh. Where does total return land?
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Rs 2.16 lakh on price alone and Rs 2.84 lakh on total return. Price compounds at 8% a year: 1.08 to the tenth is 2.16. Reinvested dividends lift the yearly return to 11%, and 1.11 to the tenth is 2.84. The gap of about Rs 68,050 is more than the Rs 30,000 that ten years of 3% seems to promise, because the dividends compound too.
Why is the answer not simply 8% growth plus 3% times ten?
Think of a bank fixed deposit with two options: interest paid out every quarter, or interest added to the deposit. The cumulative option ends with more money because each quarter's interest starts earning interest. A reinvested dividend is the cumulative option: it buys more shares, and those shares rise in price and pay dividends of their own. Adding 3% a year for ten years treats the dividend like the payout option on a fixed base, which undercounts twice: the base keeps rising and the reinvested money keeps compounding.
Rs 1 lakh reaches Rs 2.16 lakh on price alone, Rs 2.59 lakh if the 3% dividends are taken in cash and added up, and Rs 2.84 lakh if they are reinvested, and the shaded gap between price and total return widens every year. Where does the gap come from, piece by piece?
Split it into two layers. Dividends taken in cash are 3% of a price that grows 8% a year, so they start at Rs 3,000 and end near Rs 6,000, adding to about Rs 43,460 over ten years. Reinvesting them adds a further Rs 24,590, the return earned on dividends already received. So the Rs 68,050 gap is roughly two thirds the dividends themselves and one third compounding on them, and the second layer grows fastest in the later years.
The relationshipg price growth, 8% a year y dividend yield on the start of year price, 3% n years held, 10 What it says in wordsWith dividends reinvested, each year's return is price growth plus yield, and that combined rate compounds.What does this change about how you compare stocks?
Compare on total return, always. A high-yield stock with slow price growth can beat a faster grower on the number an investor keeps, and a price chart alone hides that. Index providers publish total return versions of their indices for exactly this reason. The limits are worth one sentence: tax on dividends leaks some of the gap, and reinvesting assumes you can buy at a fair price each year.
Where candidates lose it
The common wrong answer is Rs 2.46 lakh: price growth plus 30% of the starting amount. It treats the dividend as paid on a frozen Rs 1 lakh and then left idle. Both halves are wrong, and together they understate the gap by more than half.
The quieter loss is getting 2.84 without being able to split it. Saying how much is dividends and how much is compounding on dividends shows you understand why the curves pull apart.
What the interviewer asks next
- Over thirty years at the same rates, what share of the total return comes from dividends?
- If dividends are taxed at 20% before reinvesting, what does Rs 1 lakh become?
- Why would a company with high returns on capital rather retain earnings than pay a dividend?
080A bank trades at 2.5x book value. It earns an 18% return on equity and its cost of equity is 13%. What perpetual growth rate does that price imply?Sell-side equity researchIndian brokerage research
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Before solving: with no growth at all, what price to book would this bank deserve?
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About 9.7% a year, forever. For a bank, justified price to book is ROE minus growth over cost of equity minus growth. Setting 2.5 equal to (18% minus g) over (13% minus g) gives g of 9.67%. With no growth the bank would deserve 1.38x, so about 45% of today's price is paying for growth, which needs 54% of profits retained every year.
Why does price to book depend on ROE against cost of equity?
Picture a shop that earns Rs 18 a year on every Rs 100 its owner has put in, when the owner could earn Rs 13 elsewhere for the same risk. Nobody would sell that shop for Rs 100. A bank's book value is the owners' capital, so a bank earning more on it than shareholders demand is worth more than its book, and one earning less is worth less. With no growth, every Rs 100 of book produces Rs 18 a year forever, worth 18 over 13, or {pb0_80:.2f} times book.
How do you get the growth out of the price?
Growth needs capital. A bank growing its book at g must retain g over ROE of its profits, so the dividend on each Rs 100 of book is ROE minus g, not ROE. Put that dividend into the Gordon growth modelA valuation of a stream of dividends growing at a constant rate forever: next year dividend divided by cost of equity minus growth. and the price to book falls out. Set the formula equal to 2.5 and solve: 2.5 times (13% minus g) equals 18% minus g, so 1.5g equals 14.5%, and g is 9.67%.
The relationshipROE return on equity, profit over book value, 18% COE cost of equity, the return shareholders demand, 13% g the perpetual growth rate of book value and dividends What it says in wordsPrice to book is what book earns after funding growth, capitalised at what shareholders demand after growth.For a bank earning 18% on equity with a 13% cost of equity, justified price to book is 1.38x with no growth and climbs steeply as growth nears 13%, and a market price of 2.5x book implies perpetual growth of 9.7%. Is 9.7% forever believable?
That is the question the interviewer really wants answered. A reverse valuation is only useful if you then judge the implied number. Growing book at 9.7% while paying out 46% of profits requires the 18% ROE to hold for decades, with asset quality intact. Notice how steep the curve is near the answer: a point more of growth, or a point less of cost of equity, moves the justified multiple a long way, which is why small changes in rate expectations swing bank valuations. The limitation is the model itself: one growth rate forever is a simplification, and a two-stage version is fairer to a bank growing fast today.
Where candidates lose it
Candidates reach for P/B = ROE over COE, get 1.38x, and then cannot reconcile it with the 2.5x on the screen. That formula is only the no-growth case. The market price is telling you the growth, and the job is to get it out.
The algebra is the second loss: people cross-multiply and drop a sign. Write 2.5 times (0.13 minus g) on paper before you move anything across.
What the interviewer asks next
- If the cost of equity rises to 14%, what growth does 2.5x now imply?
- What ROE would justify 2.5x with only 6% growth?
- Why does a bank trading below book not automatically make it cheap?
081A retailer pays Rs 12 crore a year in store rent on a ten-year lease. Under Ind AS 116 the rent is capitalised as a lease. What happens to EBITDA, EBIT, net debt and EV/EBITDA?Sell-side equity researchIndian brokerage research
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Before any maths: which way does EV/EBITDA move once the lease is capitalised?
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EBITDA rises by the full Rs 12 crore, EBIT by about Rs 4.3 crore, net debt by a lease liability of about Rs 77 crore, and EV/EBITDA falls from 10.0x to 9.40x. Rent leaves operating costs and returns as depreciation of Rs 7.7 crore and interest of Rs 6.9 crore. The cash paid is identical, so the only safe comparison is between companies measured on the same basis.
Why does the rent move out of EBITDA at all?
Think of the difference between renting a flat and buying it with a home loan. The owner pays an EMI that is partly interest and partly repayment, and the flat sits on the family balance sheet as an asset with a loan against it. The lease standard treats a long lease the same way: the right to use the store becomes an asset, the promise to pay rent becomes a debt, and the rent itself disappears from operating costs. Discount ten payments of Rs 12 crore at an assumed borrowing rate of 9% and the lease liabilityThe present value of the lease payments still to be made, carried on the balance sheet like a loan. is Rs 77.0 crore.
What replaces the rent in the income statement?
Two lines, both below EBITDA. The right-of-use assetThe asset recognised for the right to use a leased item, depreciated over the lease term. of Rs 77.0 crore is depreciated over ten years, Rs 7.7 crore a year, and the liability accrues interest at 9%, Rs 6.9 crore in year one. So EBITDA gains the whole Rs 12 crore, EBIT gains only Rs 4.3 crore, and year-one pre-tax profit actually falls by Rs 2.6 crore, because interest is heaviest while the liability is largest. Over the ten years the charges add up to Rs 120 crore, the same as the rent; only the timing moves.
Capitalising a Rs 12 crore rent lifts EBITDA from Rs 60 crore to Rs 72 crore and EBIT from Rs 40 crore to Rs 44.3 crore, trims year-one pre-tax profit to Rs 19.4 crore, adds Rs 77.0 crore of lease liability to net debt, and cuts EV/EBITDA from 10.0x to 9.40x. The relationshipL the lease liability, the present value of ten rent payments 1.09 one plus the assumed borrowing rate of 9% 600 enterprise value before the change, equity 400 plus net debt 200 What it says in wordsThe lease becomes debt at its present value, and the rent is added back to EBITDA, so both halves of the multiple change.Why does this matter when you compare two retailers?
Because the multiple now depends on whether a company rents or owns its stores. A retailer that leases every store will look cheaper on EV/EBITDA and more levered on net debt to EBITDA than an identical one that owns its stores, unless you put both on the same basis. Here leverage rises from 3.33x to 3.85x while the multiple falls. Say which basis you are using, and either include leases for everyone or strip them out for everyone. The standard's exemptions for short-term and low-value leases also vary in use, so check the notes before comparing.
Where candidates lose it
Candidates get EBITDA right and then stop, or say EV/EBITDA goes up because debt went up. The answer needs both halves: the numerator gains the liability, the denominator gains the full rent, and the denominator gains more in proportion.
The quieter miss is saying profit is unchanged. Over the lease it is, but in year one the interest makes total expense exceed the rent, so reported earnings dip early and recover later.
What the interviewer asks next
- What happens to operating cash flow and financing cash flow in the cash flow statement?
- How would you compare this retailer with one that owns its stores?
- Why does year-one profit fall even though cash paid is the same?
082A company earns net income of Rs 200 crore on 100 crore shares. It has a Rs 300 crore convertible bond paying 8% that would convert into 15 crore shares, and the tax rate is 25%. What is diluted EPS?Sell-side equity researchBuy-side equity research
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Which diluted EPS is right?
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Diluted EPS is about Rs 1.90, against basic EPS of Rs 2.00. Assume the bond converts. Earnings rise by the after-tax interest no longer paid: Rs 300 crore at 8% is Rs 24 crore, Rs 18 crore after tax. Shares rise by 15 crore. Rs 218 crore over 115 crore shares is Rs 1.90, a dilution of 5.2%. Check first that the bond dilutes at all.
Why do earnings go up when the bond converts?
Imagine a friend who lent you money and agrees to take a share of your business instead of repayment. From that day you stop paying them interest, so your profit rises, but you now split it with one more owner. A convertible works the same way: conversion removes the coupon and adds the shares, and the if-converted methodThe standard way to include a convertible in diluted EPS: assume it converts at the start of the year, add back its after-tax interest and add the new shares. captures both. The add-back is after tax, because the interest was saving tax: Rs 24 crore of interest cost only Rs 18 crore of profit.
Assuming conversion adds Rs 18 crore of saved after-tax interest to Rs 200 crore of earnings and 15 crore shares to 100 crore, so diluted EPS is Rs 1.90 against basic Rs 2.00, and forgetting the add-back gives Rs 1.74. When would you leave the bond out altogether?
When including it would raise EPS. Work out what the bond costs per new share: Rs 18 crore of after-tax interest over 15 crore shares is Rs 1.20 a share. If that figure is below basic EPS, conversion dilutes and the bond goes in; if it is above, the bond is antidilutiveA security whose assumed conversion would increase EPS. Accounting standards exclude it from diluted EPS. and is left out. Here Rs 1.20 is below Rs 2.00, so it goes in. If the same bond converted into only 5 crore shares, its cost per share would be Rs 3.60 and it would be excluded.
The relationship200 net income, Rs crore 300 x 8% x (1 - 25%) after-tax interest saved if the bond converts, Rs 18 crore 115 existing 100 crore shares plus 15 crore from conversion What it says in wordsAssume conversion: earnings rise by the interest no longer paid, after tax, and the share count rises by the conversion shares.An analyst uses diluted EPS for valuation because a convertible that is in the money will convert, and the market prices the stock on the larger share count. The limit is that diluted EPS is a snapshot: it counts only securities that dilute at today's numbers, and a rise in the share price can bring more of them in.
Where candidates lose it
The fast wrong answer is 200 over 115, Rs 1.74: counting the new shares but forgetting that the coupon goes away. The second wrong answer adds back the full Rs 24 crore of interest instead of the Rs 18 crore after tax.
The third miss is skipping the antidilution test. Saying the per-share cost of the bond, Rs 1.20, against basic EPS of Rs 2.00 takes five seconds and shows the interviewer you know when the rule flips.
What the interviewer asks next
- The bond converts into 5 crore shares instead. What is diluted EPS?
- The company also has 10 crore options at a strike of Rs 20 with the share at Rs 40. How do they enter diluted EPS?
- Why might an analyst use diluted shares in a valuation even when the accounts show basic?
084Each year a company signs a new batch of customers who spend Rs 100 in their first year, and every batch keeps 70% of its previous year's spend each year after. With equal batches every year, what is revenue in year three, and what share of it comes from new customers?Sell-side equity researchBuy-side equity research
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Revenue is 100 in year one and 170 in year two. What is it in year three?
Show the worked solution
Revenue is Rs 219 in year three, and Rs 100 of it, 46%, comes from new customers. The three layers are the new batch at 100, the year-two batch at 70 and the year-one batch at 49. Growth falls from 70% to 28.8% even though the company signs just as many customers, because revenue creeps towards a ceiling of Rs 333, which is new spend divided by the share lost each year.
Why do you build revenue layer by layer?
Picture a gym that signs 100 members every January, where 30% of any class drops out each year. Its member count is not 100 a year times the years open; it is this year's class plus what is left of every earlier class. Revenue built from customers is a stack of cohortsA group of customers who joined in the same period, tracked together over time., each decaying at the retention rate, and the total is the sum of the layers. Writing the layers down stops you from projecting last year's growth rate forward, which is the mistake the question is set up to catch.
Each year's batch adds Rs 100 and older batches keep 70% of the previous year's spend, so revenue climbs 100, 170, 219, 253 and 277, flattening towards a ceiling of Rs 333 as growth slows from 70% to 9%. Why does growth slow when the company is signing just as many customers?
Because the loss grows with the base. In year three the company loses 30% of 170, which is 51, and adds 100, so net growth is 49. Revenue stops growing when the spend lost each year equals the spend added, which here is at Rs 333: 100 divided by 0.3. Retention sets that ceiling. At 80% retention, year-three revenue would be Rs 244 and the ceiling Rs 500; at 60% the ceiling is Rs 250.
The relationshipR_3 revenue in year three 0.7 the share of last year's spend each batch keeps R_infinity the ceiling revenue approaches with equal batches forever What it says in wordsRevenue is a geometric sum of shrinking layers, and it can never exceed new spend divided by the share lost each year.What does an analyst do with the 46%?
It tells you how much of the business must be won again every year. When nearly half of revenue comes from customers signed in the last twelve months, sales hiring and marketing spend are carrying the top line, and any slowdown in new wins shows up in revenue almost at once. By year five the share from new customers falls to 36% as the older layers pile up. The limitation of the model is equal batches: a company that grows its sign-ups each year will show faster growth, and one that spends more per customer in year two, through upsell, can see a batch grow rather than decay.
Where candidates lose it
Candidates grow revenue at the year-two rate, 70%, and reach 289, or keep adding 70 and reach 240. Both treat the business as if customers never leave. The question is testing whether you see the layers.
The second loss is missing the ceiling. Saying that revenue tends to 100 over 0.3 shows you can read what retention does to the long-run size of the business, which is the real point.
What the interviewer asks next
- What retention would you need for revenue to reach 500 in the long run?
- If each batch spends 10% more in year two before decaying, how does the picture change?
- How would you spot deteriorating retention in reported numbers when the company does not disclose cohorts?
086Ten analysts each forecast a company's EPS. Every forecast is unbiased, the errors are independent and all the same size. You pick the highest of the ten. On average, how far above the true EPS is it?Sell-side equity researchHedge fund long/short
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Each forecast is unbiased. Is the highest of the ten biased?
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About 1.54 standard deviations too high. Each forecast is right on average, but choosing the highest selects for the biggest positive error. The expected maximum of ten independent draws from a normal distribution is 1.54 standard deviations above the mean. If each analyst's error has a spread of Rs 2 around a true EPS of Rs 50, the top forecast averages Rs 53.08.
Why does choosing the highest create bias when nobody is biased?
Weigh yourself on ten bathroom scales, each accurate on average but each a little off, and write down only the heaviest reading. You will always look heavier than you are. The bias is not in any one estimate; it comes from the choosing, because the maximum picks whichever estimate had the largest positive error. Auction theory calls the same effect the winner's curseThe tendency for the winning bid in an auction to overestimate the value of the prize, because the highest estimate of many noisy ones is usually too high.: the bidder with the highest estimate wins, and usually overpaid.
Ten unbiased estimates spread around a true EPS of Rs 50 average out to Rs 50, but the highest of them sits 1.54 standard deviations above it, about Rs 53.08, so choosing the top number builds in optimism. How do you get to 1.5 without tables?
Ask where the maximum has an even chance of landing. All ten estimates must fall below a level for the maximum to fall below it, so you need the level where the chance for one estimate, raised to the tenth power, is one half. That single-estimate chance is 0.5 to the power one tenth, about 0.933, which a normal table puts at 1.50 standard deviations. The mean of the maximum is a touch higher, 1.54, because the distribution of the maximum has a longer right tail. Either number is a fine answer in the room if you show the route.
The relationshipPhi(x) the chance one estimate lands below x standard deviations 10 the number of independent estimates sigma the standard deviation of each analyst's error What it says in wordsThe maximum of ten is below a level only if all ten are, which puts its middle near 1.5 standard deviations and its average near 1.54.Where does this bite an analyst?
Anywhere the top of a list is chosen after the fact. The most bullish forecast in the consensus, the best of ten back-tested strategies and the top-ranked fund of the year all carry a selection premium that will not repeat. The effect grows with the list: the highest of five is 1.16 standard deviations high, of twenty about 1.87. The fix is to shrink the chosen number back towards the average in proportion to how noisy the estimates are. The limit of this answer is the independence assumption: analysts who talk to the same management team share errors, and correlated errors shrink the gap.
Where candidates lose it
Most candidates say zero, reasoning that averaging unbiased numbers gives an unbiased number. That is true of the average and false of the maximum. The question is built to see whether you notice the selection.
The second loss is saying biased upwards without a size. Reaching 1.5 standard deviations through the one-half route turns a hunch into a number the interviewer can check.
What the interviewer asks next
- How would the answer change with twenty analysts instead of ten?
- If the analysts' errors are correlated, does the bias grow or shrink?
- How would you adjust the best back-tested strategy's return before trusting it?
