The private-bath premium is measured, not assumed. We compare private-bath against shared-bath rooms inside the same house — same street, same landlord, same month — so the market is held constant. Median +32.7% across 97 houses carrying both room types. Comparing all private-bath rooms to all shared-bath rooms nationally instead gives a higher figure, but that measures which cities have private baths rather than what the bathroom earns. Three markets currently have enough houses for their own local figure; everywhere else uses the national one and is labelled as such. See methodology.