Changes in angular momentum in the time periods t = 1−2 Gyr (top) and t = 2−3 Gyr (bottom) for the gS0, gSa, and gSb models. The initial angular momentum L here corresponds to t = 1 and t = 2 Gyr, respectively. The time averaged value of the bar’s CR and 2:1 OLR are shown by the dotted-red and solid-blue lines. It is evident that the bars are the most effective drivers of radial migration through their CR, despite the fact that they are not transient, but only slowly evolving. This is true for the entirety of the simulations, as this figure shows.