Histogram of all 65−75 keV electron increases during in situ shock crossings divided into cases of strong ion contamination (left), increases due to a solar event (middle), and real shock-accelerated increases (right). The chart furthermore divides the numbers as a function of the different shock sources: SIR (yellow), ICME (green), SIR/ICME mixture (red), and “other”, not clearly defined sources (gray).