In just over three decades, 62% of US giants lost the top spot in their sector

The giants of the US stock market are staying on top longer, but that does not mean they are safe. A Boston Consulting Group study released in November 2026 shows that turnover among the ten largest companies in each sector fell from 24% to 13% and that, even so, most of the companies that reached that group dropped out of it at some point. For decision-makers, years without a threat do not prove strength and may only mean that no one has tried yet.

What happened

BCG analyzed the 2,000 companies with the highest market value listed on US exchanges, across 15 sectors, from 1990 to 2025. The central measure is what the study calls giant turnover, meaning the share of the combined value of a sector's ten largest companies that belongs to companies that were not in that group five years earlier.

Median turnover fell from 24% in 1990–2004 to 13% in 2005–2025. The decline showed up in 10 of the 15 sectors. In retail, for example, it went from about 10% to 4%, as waves of change favored companies already operating at large scale.

The other side of the data is what gives the story its weight. Over 35 years, 62% of the companies that made it into their sector's top ten left it at some point. Of those exits, 78% came from being overtaken by rivals and 16% from mergers and acquisitions.

Why it matters

The study separates stability from strength. A leader can stay on top for a long time for good reasons, such as scale, brand, distribution and data that reinforce one another over time. It can also stay there for less reassuring reasons: the sector is hard to enter, customers are slow to switch suppliers, or no challenger has found the way in yet.

The warning sign is in new value. In some sectors, leaders remain large but capture a smaller share of growth. In the IT sector, the five largest companies took almost 70% of the new value created from 2015 to 2025, while in other sectors long-standing leaders watched new markets go to other companies. Current size and share of what is growing are different things, and it is the second that decides the future.

What changes for you

For owners and boards, the question "are we the leader?" gives way to another: "are we capturing the sector's new growth?" A company that dominates today's market and loses tomorrow's is in decline, even if revenue does not show it yet.

For sales leaders, the data points to where to look. Growth that comes only from the legacy base of customers and products signals that the company is defending its position. When your company is the challenger, the study points to customers, margins, channels or models the leader finds unattractive.

For those who run operations, scale is an advantage as long as the rules of the game hold. When they change, the same structure can become a burden. It pays to know which parts of the operation sustain the advantage and which only sustain size.

What changes in Brazil

For most Brazilian companies, which do not lead their own sectors, the study is more useful read from the challenger's side. Markets in which a few groups concentrate scale, brand and distribution can look stable for a long time, and the spaces the largest players ignore may be the way in.

Companies that already lead a regional niche can apply the study's own question and check whether the position was won or has simply not been contested yet. The figures come from the US stock market. Whether the top of Brazilian sectors turns over at the same pace is something each company can observe in its own market.

The play

1. Measure your share of growth, not just of the market. Break out revenue from products, customers and channels that did not exist three years ago. If that slice is small, the company is living off the past.

2. List the bets that sustain your advantage. Scale, price, relationships, brand or technology: write down what your position rests on and what happens if a competitor changes the rules instead of playing better. This is the third test the study proposes for leaders.

3. Map where the leader does not want to play. If your company is a challenger, look for the customer, margin or channel the largest players ignore. Use that space to build the capabilities that will count in the next contest.

The other side

Market value is an imperfect yardstick, because it reflects investor sentiment, not just business performance. And the sample, made up of large publicly traded US companies, leaves out private companies and other countries.

The study itself adds caveats. Competitive advantage belongs to the company, not the sector, and sector averages can hide large differences between companies. Part of the decline in turnover at the top, as with digital platforms, reflects the emergence of a new category rather than greater stability alone. And a long run at the top may signal real advantage, good adaptation or a market that simply has not been challenged yet. The data does not say which of the three applies to you, and that answer requires looking inward.