The “Inevitability Test”: How to Find Stocks That Are Almost Impossible to Kill
Most investors ask if a company can grow. The better question is whether it can survive.
There’s a question Warren Buffett has been asking for over 50 years before he buys a single share.
Not “what’s the upside?” Not “what’s the growth rate?”
The question is simpler and far more powerful:
Is this business inevitable?
Meaning: Could this company still dominate its industry 20 years from now, even if a well-funded competitor tried everything to take it down?
If the answer is yes, you might have something worth owning for a long time.
If the answer is “maybe” or “it depends,” that’s worth understanding before you put real money to work.
Here’s how to find out.
What Buffett Actually Means by a “Moat”
Buffett didn’t invent competitive advantage. But he gave it a name that stuck.
He calls it an economic moat. It’s the business equivalent of the water surrounding a castle. The wider the moat, the harder it is for competitors to get in. The deeper it is, the more painful it is to try.
His exact words from a 1995 Berkshire shareholder meeting:
“What is keeping that castle standing? And what’s going to keep it standing — or cause it not to be standing — five, ten, twenty years from now?”
That’s the whole framework. Everything else is just detail.
The 6 Fundamentals to Look For
Before you buy, run any stock through these six filters. They’re not magic. But they separate durable businesses from ones that just look good in a bull market.
1. Pricing Power
Can the company raise prices without losing customers?
This is the single biggest signal of a durable business. Companies without pricing power are at the mercy of inflation, competition, and economic cycles. Companies with it can pass costs along and protect their margins.
The test: Has gross margin stayed stable or improved over the last 5–10 years, even during downturns?
Classic example: Coca-Cola has raised prices repeatedly for decades. People still buy it. That’s pricing power. Compare that to a commodity airline. The moment a competitor drops fares, customers switch tonight.
2. Switching Costs
How painful is it for a customer to leave?
The best businesses make leaving feel like a root canal. Not because they’re trapping customers, but because they’ve become so embedded in how people work and live that switching is genuinely expensive.
The test: Would a customer have to retrain staff, migrate years of data, or rebuild workflows to switch providers?
Classic example: Microsoft Office. Businesses have been using Excel and Word for 30 years. The switching cost is more painful than any fee. It’s thousands of hours of retraining and migration. That’s a moat. A wide one.
3. Network Effects
Does the product become more valuable as more people use it?
This is the rarest and most powerful moat type. When every new user makes the product better for existing users, growth compounds the advantage, and competitors face an almost impossible task of replicating it from scratch.
The test: Does the product’s value depend on the size of its user base?
Classic example: Visa. Every new cardholder makes Visa more attractive to merchants. Every new merchant makes Visa more valuable to cardholders. No startup can replicate that network because it took decades to build.
4. Is Return on Equity (ROE) Consistently Above 15%?
This is where the moat shows up in the numbers.
ROE measures how much profit a company generates relative to shareholder equity. A consistently high ROE above 15% over five or more years is one of the strongest signals that a real competitive advantage exists.
The test: Pull up 5–10 years of ROE. Is it consistent? Or does it spike in good years and collapse in bad ones?
Classic example: Apple’s ROE has been well above 100% in recent years, which is a reflection of its brand power, ecosystem lock-in, and pricing authority all compounding together. That’s not luck. That’s a moat.
5. Free Cash Flow — The One Number That Doesn’t Lie
Revenue can be massaged. Earnings can be adjusted. Free cash flow is harder to fake.
It tells you whether the business actually generates real money after paying for the things it needs to keep running. Buffett has said he looks for businesses that generate strong free cash flow without requiring constant reinvestment just to stay competitive.
The test: Is free cash flow growing year over year? Is it being used to buy back shares, pay dividends, or build the business? Not just keep the lights on?
Classic example: A great business like Visa generates enormous free cash flow because it doesn’t need factories, inventory, or constant R&D just to maintain its position. A bad business generates revenue but burns it all on reinvestment to survive.
6. The 10-Year Competitor Test
This one is qualitative, but don’t skip it.
Imagine a well-funded, intelligent competitor shows up tomorrow with unlimited capital and a mission to destroy this company. What happens?
If your answer is “they’d probably win eventually”, that’s a red flag. If your answer is “they’d spend billions and still fail”, that’s a moat.
The test: What would it actually take to replicate this company’s advantage? Patents? 50 years of brand building? A global network of 100 million users? The harder the answer, the better.
Classic example: Could a competitor build a better search engine than Google? Technically, maybe. But Google’s advantage is massive. It’s 25 years of data, user habits, and advertiser relationships are almost impossible to replicate from scratch.
Why This Matters More Than Ever Right Now
In a market full of AI hype and 80x earnings multiples, it’s tempting to chase growth.
But the investors who compound wealth over decades aren’t the ones who found the hottest trade. They’re the ones who never got wiped out.
That starts with a simple question before every purchase:
Is this business inevitable, or just popular?
Buffett put it plainly: “The key to investing is determining the competitive advantage of any given company, and above all, the durability of that advantage.”
Run the checklist. Know what you own. That alone puts you ahead of most retail investors.
The best investments don’t feel exciting. They feel obvious…in retrospect. Find the ones that are obvious right now.