Comparison of the polarization fraction computed through the GK method (solid line) and the radiation anisotropy method we employ in this paper (dotted line). For more details on the simulation parameters, see Goldreich & Kylafis (1981). We consider a J = 1 − 0 transition at 100 GHz, with a strong magnetic field along the -axis and a velocity gradient of 10⁻⁹ s⁻¹ in the xy-plane. We consider a temperature of T = 10 K. Three ratios for the collision-radiative rates are considered and denoted inside the figure. The polarization fraction was computed for a ray traveling along the -axis.