R² (top) and power-law index (bottom) of the fits of various GMC properties (as a function of the Hα luminosity of the matched H II region) against the MOP. The fitted GMC properties are, from left to right: the molecular mass, the peak temperature, the surface density, and the characteristic turbulent linewidth. Blue (respectively red) lines show an increase (respectively decrease) of the R² coefficient with the MOP. The uncertainty intervals are computed using a standard bootstrap method.