Beaming factor η as a function of geometric albedo p_V for the entire sample, compared with Monte-Carlo simulations assuming a rotation period of 8 h, a random orientation of the polar axes, uniform on the sphere, and a random distribution of surface roughnesses. The synthetic objects have the same r_h values as in the observations. Cases with (i) a constant thermal inertia Γ = 2.5 MKS (red points) and (ii) Γ = 2.5 MKS for objects with p_V < 20% and Γ = 0.5 MKS for objects with p_V > 20% (green points) are shown. The latter case allows an improved match of the observations, except for Makemake (p_v = 0.77 ± 0.02, ).