Fraction of ageing, quenched, and retired galaxies as function of stellar mass in redshift bins. Each row of panels shows fractions inferred using BESTA for Euclid (top) and IllustrisTNG (middle) samples, along with true fractions from IllustrisTNG (squares). The error bars were estimated from 1000 random samples, each selecting 20% of the total sample and computing the 5 and 95 percentiles. In the top row, fractions for masses below the mass completeness limit (see Appendix A) are shown as dotted lines. Similarly, in IllustrisTNG, masses below the retired resolution limit are represented as dotted lines.