Distributions of the power law index for the Fe II velocity of GRB-SNe and ordinary type Ic-BL SNe. For broken power laws, the decay index of the first segment is plotted. Fit results for the sample of type Ic SNe from Modjaz et al. (2016) are shown for comparison purposes. Left: Histograms of Fe II decay indices including data from the Gold, Silver, and Bronze samples. Right: Histograms of Fe II decay indices including data from the Gold sample only. Allowing for the low population statistics, the decay index appears to be very similar for type Ic SNe, ordinary type Ic-BL SNe, and GRB-SNe. This indicates that the presence or absence of a central engine or a relativistic jet has no impact on the rate of velocity evolution of a supernova.