ForecastingStocks

Past growth is history. As an investor you are buying the future, so the most valuable judgement is how much room a company still has to grow — its runway.

The size of the opportunity

The key idea is the total addressable market (TAM) — how big the company's market could ultimately become. A business with 2% of a vast, expanding market has a long runway ahead; a business with 60% of a shrinking one is near the end of its road, no matter how good it looks today.

Ask:

How large is the market, and is it growing or shrinking? Riding a structurally growing market is the easiest tailwind there is.
How much of it does the company already have? Low penetration of a big market is the sweetest spot.
Can it expand into adjacent markets? The best growth stories add new products, new geographies or new customer types without losing focus.

Reinvestment — the quality of the runway

A long runway is only valuable if the company can fund its growth at attractive returns. The strongest compounders generate cash and plough it back into the business at high rates of return, so growth pays for itself rather than relying on debt or constant share issuance. A company that must keep borrowing or selling new shares to grow is buying a runway it cannot really afford.

Beware the story stock

Runway is where investors most often get carried away. A huge "market opportunity" in a pitch deck is not the same as a realistic path to capturing it profitably. Discount grand claims, look for evidence the company is already winning share, and remember that the price you pay for that future growth is decided in the Valuation track — optimism is not free.