Typical pareto rule I've found. It'd be closer to 99% if all of their supply was sold into the exchanges, but most sites have a much more complicated waterfall

Typical pareto rule I've found. It'd be closer to 99% if all of their supply was sold into the exchanges, but most sites have a much more complicated waterfall to clear out their supply such that the premium inventory gets direct sold or sold into a private marketplace and only the remnant inventory goes into public exchanges.