Upper panel: reconstructions of the redshift distributions for increasing catalogue sizes. Coloured bands show the 90% credible intervals for the light (red) and heavy (golden) populations. Solid lines indicate the median reconstructions, while dashed lines mark the true distributions. For the heavy population, the dashed and full lines superimpose almost perfectly. Lower panel: distribution of within-population and between-population KS statistics. The value on top shows the probability that the two heavy and light population have different redshift distributions.