X-ray light curves of low-, intermediate-, and high-L SN-GRBs. Overlaid is the evolution of the observed luminosity distribution of 273 long Swift GRBs for which a SN search was not feasible or unsuccessful (i.e. GRBs 060505 and 060614). These were discovered between December 2004 and February 2014. The colour table on the right side translates a grey shade at a given luminosity and time into a fraction of bursts. The inset displays the observed luminosity distribution at 0.5 days (dotted vertical line). The vertical lines in the inset show the luminosity of the intermediate-L GRB 120422A and the low-L GRBs  031203, 060218, and 100316D.