Reverse DCF

Chapter 20 ended with a problem: a DCF is a machine for converting your assumptions into a number, and your assumptions are the weakest part. This chapter runs the machine backwards, and in doing so removes you from it.

The inversion

A normal DCF asks: given my forecast, what is this worth?

A reverse DCF asks: given today's price, what must this company do?

Same arithmetic, opposite direction. You hold the price fixed, hold the discount rate at something defensible, and solve for the growth rate that makes the two agree.

The output is not a valuation. It is a statement of what the market is already assuming — and that is a far better thing to have, because judging whether an assumption is plausible is much easier than producing a forecast of your own.

Why this is the better question

Three reasons, and the first is the important one.

It removes your optimism. You are no longer forecasting; you are assessing someone else's forecast. People are considerably better at the second task. "Will this company grow 30% a year for a decade?" is answerable from industry history. "What will this company's cash flow be in year seven?" is not.

It makes disagreement concrete. "The stock is expensive" is an opinion. "The price assumes 28% growth for ten years, and no company in this industry has sustained above 18%" is an argument with a checkable fact in it.

It identifies what to watch. Once you know the price assumes 20% growth, you know what to monitor. Each quarter either supports the assumption or erodes it, and you are watching the right thing instead of the share price.

Doing it roughly

You do not need a full model. Rearranging chapter 16's perpetuity gives a usable approximation.

A company earning ₹100 crore of free cash flow, valued by the market at ₹2,500 crore, at a 10% discount rate:

value = cash flow ÷ (r − g)
2,500 = 100 ÷ (0.10 − g)
0.10 − g = 100 ÷ 2,500 = 0.04
g = 6%

The price assumes about 6% growth for ever. Now the question is answerable: is 6% perpetual growth reasonable for this business? Against inflation, against its industry, against its history?

If the market capitalisation were ₹5,000 crore instead, the implied growth would be 8% — and for a mature business, perpetual 8% is a much stronger claim than perpetual 6%.

This takes two minutes and it reframes the entire question.

The two-stage version

Perpetual growth is a crude frame for a fast-growing company. The better form assumes high growth for a period, then a modest terminal rate, and solves for the high-growth figure.

The output then reads: the price assumes 22% growth for ten years, then 4% for ever. Which is precisely the claim you want to assess, because you can check how many companies have ever done it.

That check is usually the decisive one. High growth rates sustained for a decade are rare, and the base rate is knowable: look at how many companies in the industry managed it over the past twenty years. If the answer is almost none, the price is assuming the company will be exceptional — which may be right, and which you now know you are betting on.

What it tells you about a cheap stock

It runs both ways, and the reverse case is as useful.

A company trading at a price implying −2% growth for ever is being priced for permanent decline. Sometimes that is correct — chapter 17's value trap. Sometimes the business is stable and the market is extrapolating a bad couple of years.

Either way, the question becomes specific: is this business going to shrink for ever? That is answerable from the industry and the company's position, in a way that "is this cheap" is not.

The honest limits

The discount rate is still a judgement. Chapter 16: two points move everything. State the rate used, and show the implied growth at a couple of rates.

It assumes the current cash flow is representative. Chapter 17's cyclical trap applies unchanged. Starting from peak earnings produces an implied growth rate that is too low, and the stock looks cheap.

It says nothing about timing. The price can keep assuming something implausible for years. Chapter 2 of the equity subject: sentiment has no obligation to cooperate.

The habit

Before buying anything, answer this sentence:

At this price, this company has to _______ for me to earn a reasonable return.

Fill the blank with a growth rate and a margin, not with a feeling. If you cannot fill it, you do not know what you are buying — and if the filled version sounds implausible when read aloud, that is the analysis finished.

The point

A reverse DCF holds the price fixed and solves for the growth it implies, which removes your own forecasting from the exercise. The resulting statement — this price assumes 22% growth for ten years — can be checked against how often any company has done that. It makes disagreement concrete and tells you exactly what to monitor afterwards.