Constraints on hyperparameters of the two-population mixture model from the analysis of type Ia supernovae in the Hubble flow from the Pantheon+ compilation. The red and blue colours respectively denote the old and young populations, where the low-stretch peak is fully populated by the old population and the high-stretch peak by a mixture of both populations. The contours show 1σ and 2σ credible regions containing 68 and 95 per cent of 2D marginalised probability distributions. The inset panel shows the stretch distributions of both supernova populations compared to the measurements.