Distribution of the luminous efficiency τ in percent for different density assumptions: (a) ρ = 500 kg m⁻³; (b) ρ = 1000 kg m⁻³; (c) ρ = 1500 kg m⁻³; (d) ρ = 2000 kg m⁻³; (e) ρ = 2500 kg m⁻³; (f) ρ = 3000 kg m⁻³; (g) ρ = 3500 kg m⁻³; (h) ρ = 4000 kg m⁻³; (i) ρ = 4500 kg m⁻³. τ is plotted against the initial velocity of the events with fits through the data in semi-log space. These results were obtained from the dataset of 288 objects. Blue dots: values of τ; green dash-dotted line: weighted least squares fit (WLS) applied to the data, the method weights the values by the relative error of the value; blue dotted line: the results found by Halliday et al. (1996); magenta dash-dotted line: the results found by Ceplecha & McCrosky (1976).