Binary fraction as a function of primary mass, m_p. Points show the median across all samples, with error bars marking the 16th–84th percentile range. The dashed gray line indicates the binning scheme and median values. The last bin spans 89.73–149.17 M_⊙; its upper edge corresponds to the most massive stars found in our models, which form through mergers and are therefore single. The solid gray curve shows the best-fit model obtained via maximum-likelihood estimation. Observational results are over-plotted as open squares: Kroupa et al. (2003) for M-, K- and G-type stars (left three points) and De Rosa et al. (2014) for A-type stars (right-most point). We note that all observational results come from the Galactic field.