Strategic Economics

Cross-side Network Effects and Which Side to Subsidize

Work out which side of your platform should be charged, which should be paid to show up, and how much, from a measured externality rather than from instinct or from whichever side complains loudest.

  • Advanced
  • 14 min total
  • 13 chapters

What decision this helps you make: Which side of the market you subsidize, what you charge the other side, and how much acquisition spend each side actually justifies today rather than at launch.

What this topic is

A cross-side network effect is when adding a user to one side of a market makes the market more valuable to the people on the other side. One more driver does not help other drivers. It helps riders. One more seller does not help other sellers. It helps buyers, and usually hurts the other sellers. Because the benefit lands on the far side, the user who creates it will not pay for it, which is why platforms end up charging one side and subsidizing the other.

Why it matters

A platform has two price levers, not one: the total it charges per transaction, and how that total is split between the sides. Standard economics says only the total matters. For a two-sided platform that is false. The split changes how many users each side has, which changes how valuable the platform is to everyone. Getting the split wrong is not a rounding error; it is the difference between a market that fills and one that empties.

Who should learn it

Anyone setting fees or acquisition budgets on a marketplace, app store, payment network, ad platform, or events business, and anyone deciding whether a supply-side bounty that made sense two years ago still makes sense now.

What you will understand

  • How to measure a cross-side externality from your own fill-rate data rather than assuming it
  • The four tests that decide which side is the subsidy side and which is the money side
  • A worked repricing that looks 10% accretive in the first round and nets to zero in steady state
  • Why the correct supply subsidy decays as supply grows, and what happens if you never re-measure it

Prerequisites

Common misconception

"We should subsidize supply, because supply is the hard side." Supply is usually the hard side at the start, and almost never stays the hard side. The subsidy is justified by an externality that shrinks as the side it applies to grows: at ninety contractors an extra contractor adds real fill; at two hundred they mostly take work from the contractors already there. The bounty that was correct at launch is a standing transfer three years later, and nothing in the dashboard flags the change, because the dashboard credits each new supplier with all the volume they touch rather than with the volume that would not have happened without them.