Stellar mass–halo mass relation for the simulated galaxies. Dashed lines and solid lines show the relation obtained from Local Group data (Brook & Di Cintio 2015; Garrison-Kimmel et al. 2014). The relations are extrapolated below ∼10^6.5 M_⊙ due to sample incompleteness (dotted lines). Circles show the raw data; solid dots show the simulation data correcting for observational and simulation biases (Munshi et al. 2013) in measuring stellar and halo masses. Overall the simulations produce the right number of of stars. The most massive halo converts about 1 per cent of gas into stars. The rapid drop in SF efficiency at halo masses below 10¹⁰ M_⊙ is due to the introduction of ‘early feedback’ (see the text).