the HiBAL composite and LoBAL composite, as shown in Figures \[fig:fig3\] and \[fig:fig4\]. We note that the form of this “droop” is similar to the emission line flux decrement that was observed in quasars with large emission-line blueshifts ([Richards]{} [et al.]{} 2002b) and may be an indication that BALQSOs have larger-than-average emission-line blueshifts; see § \[sec:parent\].

In addition to this “droop” is the obvious decrement of flux blueward of the emission-line peak that is caused by the BAL troughs themselves. The absorption becomes significantly more pronounced in the HiBAL composite near the expected peak of (i.e., at zero velocity with respect to the quasar redshift); in the LoBAL composite, the change at zero velocity is even more dramatic. broad absorption troughs thus penetrate to velocities less than the minimum velocity of the balnicity index ($3000\,{\rm km\,s^{-1}}$ at 1534.5 Å). The trough in the HiBAL composite has a minimum near $1520\,{\rm \AA}$ with a weaker shoulder that extends from about $1500\,{\rm \AA}$ to perhaps as blue as the peak of +\]. The LoBAL composite difference spectrum exhibits two distinct troughs near $1502\,{\rm \AA}$ and $1541\,{\rm \AA}$ that are separated by a peak near $1518\,{\rm \AA}$ (which is roughly consistent with the 