Invisible Z width per active neutrino (${\Gamma }_{\mathrm{inv}}=N_{\nu }{\Gamma }_{\nu }$)

For equally coupled light active neutrinos, the total invisible width is the sum of the single-species widths. A three-flavor invisible width near $501$ MeV corresponds to about $167$ MeV per species. It must not be assigned to each additional neutrino separately.