Upper panel: inferred binary fraction as a function of the adopted threshold velocity (ΔRV_min) for the unevolved (dwarf/giant) B-type stars in our sample (solid line). The dashed line shows the corresponding fraction that would have been classified as binary candidates but failed the ΔRV_min criterion. Lower panel: as for the upper panel, but for the supergiants. In both plots the vertical dotted line indicates the adopted threshold of 16 km s^-1.