Left panel: peak absolute magnitude vs. distance modulus. The red empty diamonds are the simulated SNe at large distance moduli (> 37.88 mag), where the SN sample is not complete owing to the Malmquist bias (see diagonal dashed line). We followed the method by Richardson et al. (2014, see text in Sect. 8). Right panel: peak magnitude distribution before and after Malmquist-bias correction. It implies a decrease of the ⁵⁶Ni mass average of about 17%.