Glossary · Economic ideas
Network effects
A network effect is when a product gets more valuable the more people use it, like a phone, a messaging app or an online marketplace.
Also called: network effect, network externality, Metcalfe’s law, demand-side economies of scale
In plain words
One telephone is useless: there is nobody to call. Two phones make one call possible. Ten phones make 45 different pairs who can talk. Every new phone makes all the others more useful. That is a network effect.
Messaging apps, social networks, online marketplaces, payment cards, even languages work this way. You join the one your friends already use, which makes it more attractive for the next person, and so on.
Network effects can let a winner take most of a market. Once a network is big, a rival with a better product can still struggle, because its few users have no one to talk to.
Example
Why the biggest marketplace keeps winning
Picture two websites for selling used bikes.
- Site A has 1,000 sellers; site B has 100. Buyers go to A, where they are more likely to find the bike they want.
- With more buyers on A, bikes sell faster there, so new sellers list on A too.
- Each side brings more of the other: economists call it a two-sided network effect.
- A year later A might have 5,000 sellers and B 50, even if B’s website is nicer.
Size feeds on itself. That is why marketplaces, payment networks and social apps often end up with one or two giants.
One level deeper
Metcalfe’s law, named after Robert Metcalfe, a co-inventor of Ethernet, says a network’s value grows with the square of its users, since n users can make n × (n − 1) ÷ 2 connections. It is a rough rule: not every connection is worth the same, and many people only ever talk to a few others.
Network effects are like economies of scale, but on the buyers’ side: instead of costs falling as a firm grows, value rises as its user base grows. Together they help explain why some markets drift toward a monopoly.
They can also keep a standard in place long after its original reason is gone. The QWERTY keyboard was laid out for typewriters in the 1870s and survives largely because everyone has learned it: switching alone would gain you little.
Why it matters
They explain why some tech companies grew so big so fast, and why their positions are hard to attack.
They make early growth precious: a network that gets big first can keep its lead for years.
They also work in reverse: when users start leaving, the network gets less useful for those who stay, and the exodus can speed up.
A common mistake
Myth: The best product always wins.
In fact: Not in markets with strong network effects. A product your friends use can beat a better one that nobody you know uses. Quality matters, but so does who got there first.
Questions people ask
What is an example of network effects?
Telephones, messaging apps, social networks, payment cards (more shops accept a card that more people carry, and more people carry a card that more shops accept) and online marketplaces.
What is the difference between direct and indirect network effects?
Direct: each user benefits from more users of the same kind, like friends on a messaging app. Indirect, or two-sided: more users on one side attract more on the other, like buyers and sellers, or gamers and game makers.
What is Metcalfe’s law?
A rule of thumb that a network’s value grows with the square of its number of users: ten times the users means about a hundred times as many possible connections.
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About the numbers
- This page explains a term. It is not investment advice.