Modulation in the fraction of quiescent galaxies for the IllustrisTNG (namely, TNG100, red symbols) and the original Illustris (blue symbols) simulations. Error bars represent the best-fitting standard deviation, as described in the Methods. The signal is shown in green for a sample of IllustrisTNG satellites with the same mass distribution as those in Illustris, to assess the possible effect of a mass bias between the two simulations. Both simulations probe a similar ~100-Mpc comoving cosmological volume and thus share the same large-scale structure properties; the treatment of black hole growth and feedback is the most relevant difference between the two. However, it is clear that the amplitude of the modulation is much higher in IllustrisTNG (0.032 ± 0.004) than in Illustris (0.013 ± 0.007).