We have quantitatively investigated the radiation belt dynamic variations of 1.5–6.0 MeV electrons during 54 coronal mass ejection (CME)–driven storms from 1993 to 2003 and 26 corotating interaction region (CIR)–driven recurrent storms in 1995 by utilizing case and statistical studies based on the data from the SAMPEX satellite. It is found that the boundaries determined by fitting an exponential to the flux as a function of L shell obtained in this study agree with the observed outer and inner boundaries of the outer radiation belt. Furthermore, we have constructed the radiation belt content (RBC) index by integrating the number density of electrons between those inner and outer boundaries. According to the ratio of the maximum RBC index during the recovery phase to the prestorm average RBC index, we conclude that CME‐driven storms produce more relativistic electrons than CIR‐driven storms in the entire outer radiation belt, although the relativistic electron fluxes during CIR‐related storms are much higher than those during CME‐related storms at geosynchronous orbit.