Distributions of RSG and BSG plus YSG number counts (top and middle panels, respectively), as well as the number ratio of BSGs plus YSGs to RSGs (bottom panel) in logarithmic luminosity bins between 4.7 and 6.05 in log(L/L_⊙). Diamond scatter points correspond to observational samples of 147 RSGs (with log(T_eff/K) < 3.68) and 86 BSGs plus YSGs (with log(T_eff/K) between 3.68 and 4.35). Uncertainties correspond to 90% confidence limits assuming a Poissonian distribution for the number of supergiants in each bin. Only a lower limit is available for the ratio of BSGs plus YSGs to RSGs in the luminosity bin 5.6 ≲ log(L/L_⊙) ≲ 5.8. Solid-line histograms, normalized to 233 stars in total, correspond to several different sets of stellar tracks at Z = 0.0034 = 0.2 Z_⊙ metallicity.