urbanization doesn't matter either. it's indoor mixing density (which population density and urbanization poorly approximate in this case) that matters. that's again why the key mitigation is to avoid breathing others' direct exhaust, which is most directly heuristicized by distancing indoors (which implicitly addresses density, unlike masks which only help at the margins and are mostly performative due to their counterintuitive failure modes, such as every breath rehydrating and potentially dislodging virus particles otherwise caught in the mask).