▁each ▁over - the - counter ▁contract ▁has ▁to ▁be ▁uniqu ely ▁struct ured ▁and ▁could ▁involve ▁complex ▁pay - off ▁and ▁risk ▁profiles . ▁One ▁growth ▁area ▁is ▁private ▁invest ment ▁in ▁public ▁equ ity ▁( PI PE s , ▁otherwise ▁known ▁as ▁Reg ulation ▁D ▁or ▁Reg ulation ▁S ). ▁Such ▁transactions ▁are ▁priv ately ▁negoti ated ▁between ▁companies ▁and ▁acc red ited ▁invest ors . ▁ ▁B anks ▁also ▁earned ▁re venue ▁by ▁se cur it izing ▁deb t , ▁particularly ▁mort g age ▁deb t ▁prior ▁to ▁the ▁financial ▁crisis . ▁In vest ment ▁banks ▁have ▁become ▁concerned ▁that ▁l enders ▁are ▁se cur it izing ▁in - house , ▁driving ▁the ▁invest ment ▁banks ▁to ▁purs ue ▁vertical ▁integration ▁by ▁becoming ▁l enders , ▁which ▁is ▁allowed ▁in ▁the ▁United ▁States ▁since ▁the ▁repe al ▁of ▁the ▁G lass – Ste ag all ▁Act ▁in ▁ 1 9 9 9 . ▁ ▁Top ▁ 1 0 ▁banks ▁▁ ▁According ▁to ▁the ▁Fin an cial ▁Times , ▁in ▁terms ▁of ▁total ▁advis ory ▁fe es ▁for ▁the ▁whole ▁of ▁ 2 0 1 8 , ▁the ▁top ▁ten ▁invest ment ▁banks ▁were : ▁Many ▁of ▁these ▁fir ms ▁belong ▁either ▁to ▁the ▁Bul ge ▁Bra cket ▁( upper ▁tier ), ▁Middle ▁Market ▁( mid - level ▁business es ), ▁or ▁are ▁bout ique ▁invest ment ▁banks ▁( special ized ▁business es ). ▁ ▁The ▁above ▁list ▁is ▁just ▁a ▁ranking ▁of ▁the ▁advis ory ▁arm ▁( M & A