The median ex situ stellar mass fraction as a function of stellar mass M_*, calculated for galaxies at z = 0. The red and blue lines show the correlation (at a fixed stellar mass) with respect to various galaxy properties, which are divided into three broad categories: stellar properties (left), morphology (middle), and halo assembly (right). These galaxy properties are described in detail in Section 4.2. The shaded regions indicate the 16th to 84th percentile ranges. The blue diamond in the upper-right panel corresponds to the Milky Way-like galaxy studied in Zhu et al. (in preparation), which has a relatively early formation time.