EMs plotted against DMs for the 63 PSRs included in our sample. Filled symbols correspond to EMs values derived from radio continuum spectral turnovers in K17 (pentagons), J18 (circles), K21 (squares), and S22 (triangles). Open blue symbols represent EMs values predicted by the NE2001 model (Cordes & Lazio 2002, 2003) for our collection of PSRs, while the smallest blue points indicate values derived for all PSRs in the ATNF catalogue. The diagonal dotted lines show the relationship for constant size values, as labelled.