Frequency evolution in W₅₀ of 16 pulsars classified (in Rankin 1983a) as exhibiting conal-single profiles. Power-law fitting of the high-frequency width measurements is indicated by solid lines, and their extrapolation to low frequencies is indicated by dashed lines. Intermediate-frequency measurements (the absorption part) fall below the extrapolated high-frequency fit and are indicated by solid, connected line segments. In group (a), each panel shows the comparison between our results and those of Rankin (1983b). The upper data are our results, and the data in the bottom (red) are the results given by Rankin (1983b). Group (b) is our newly added results of frequency evolution in W₅₀ for 12 pulsars.