Resolves positively if, by 2030-12-31, 75% or more of US residential homes are sold without an intermediary (a realtor). Online exchanges do not count as an intermediary for purposes of this market, except if they employ human brokers that typically spend 2 hours or more on each transaction.

I will use whatever sources seem most credible in resolving this market. A few example sources that suggest residential real estate is not currently disintermediated are the National Association of Realtors (which says 85%+ of 2022 residential real estate transactions were brokered), the Close (which appears to be a real estate newspaper and says that 92% of residential real estate transactions were brokered), and also personal experience, where most people I know use a realtor when selling their house.

If several respectable news organizations report that over 75% of US residential homes are sold sans intermediary, that would be pretty convincing for me to resolve positively.