Normalized distributions of the logarithm of BI measured from C iv troughs. The BI distribution from the present catalog (black histogram) computed from 7227 visually flagged BAL quasars is very similar to the distribution from Trump et al. (2006, red histogram) obtained from 1102 BAL quasars from the SDSS-DR3 quasar catalog (Schneider et al. 2005). The distribution is also very similar to the BI distribution from Allen et al. (2011, blue histogram) based on the SDSS-DR6 quasar catalog.