Evolution of the parameter σ as a function of redshift, obtained by fitting a log-normal function to the 1/V_max data. Each color corresponds to a stellar mass bin (blue: 9.5 < log (M⋆) < 10, green: 10–10.5, red: 10.5–11 and black 11–11.5). The shaded areas correspond to the value measured when all the sSFR functions are combined at z = 0 as shown in Fig. 8. The individual σ points are not measured at 9.5 < log (M⋆) < 10 since we set the value of σ in this mass range.