Changes in Fig. 6 due to the use of different bin sizes in the selection procedure. In addition to our standard choice of 2a (middle two columns here), in the first two rows we also consider a bin size of a (columns 1 − 2) and 3a (columns 5 − 6) for the gSb and gSa models and earlier and later times, as indicated. The bottom row shows the effect of a constant bin size of 1, 2, and 3 kpc for the gSb model. The overall behavior is preserved in all cases.