A sector is a broad industry group — Technology, Health Care, Energy, and so on — used to sort companies by what they mostly do. On MarketCapLens, each sector page ranks the companies in that group by market capitalization, largest first.
Key takeaways
Comparing Apple to a regional bank is rarely useful. Sectors give you a fairer neighborhood: chipmakers next to software firms, insurers next to banks. Indexes, funds, and research notes all use some version of this map (often GICS-style labels). MarketCapLens uses the sector tags that come with the market data so the ranking and the sector hubs stay consistent.
A company’s market cap is price × shares. A sector’s market cap is simply those company figures added up.
Sector market cap = sum of members' market caps
Imagine a tiny “sector” with three companies:
| Company | Market cap | Weight in sector |
|---|---|---|
| Alpha | $600B | 60% |
| Beta | $300B | 30% |
| Gamma | $100B | 10% |
| Sector total | $1T | 100% |
Alpha alone is more than half the sector. If Alpha’s shares jump 5% and the others are flat, the sector total moves even though two of three companies did nothing. That’s why sector pages show both the ranked list and each company’s weight — so you can see concentration, not just a name list.
The same denominator idea applies to the whole ranking. A sector's share of tracked market cap is that sector's combined cap divided by the combined cap of every company MarketCapLens ranks, not divided by the count of sector names. Ten equal names would each be 10% of a 10-name neighborhood. They would be a much smaller slice of a 2,000-name universe. Open the sectors hub for the live split; this page does not freeze those weights.
On the live Technology page, a handful of names — NVIDIA, Apple, Microsoft — account for a large share of the sector total. That is the table above in real life. Novo Nordisk plays a similar role on Health Care: one large company moves the group more than a long tail of smaller members.
A sector ranking is not a recommendation, and “largest sector” is not “best sector.” Size describes how much equity value sits in that group right now. For how we build the underlying list of companies, see How the MarketCapLens Ranking Works.
For general education only. Nothing here is investment advice.
Formulas and worked examples are MarketCapLens's. See who checks the numbers.