Empirical relationships between the maximum proton flux at 25 MeV and (left) the GOES X-ray flux as well as (right) the LASCO plane-of-sky CME speed for SEP events detected at Earth between December 2006 and February 2018. The plot distinguishes between near-sided (red) and far-sided (blue) events. The best-fit curves shown in green are applied to the near-sided data only. The top left corner of both panels shows the corresponding equation for the best-fit curve and the Pearson correlation coefficient.