▁bond ▁offering ▁were ▁too ▁high ▁for ▁short ▁m atur ities ▁to ▁be ▁practical . ▁G MA C ▁thus ▁began ▁to ▁sell ▁their ▁notes ▁directly ▁to ▁invest ors . ▁Because ▁of ▁ill iqu id ity ▁of ▁the ▁secondary ▁market ▁and ▁se cur ities ▁reg ulations , ▁the ▁market ▁remained ▁relatively ▁quiet ▁until ▁ 1 9 8 0 s . ▁ ▁Then , ▁in ▁ 1 9 8 1 , ▁invest ment ▁banks ▁stepped ▁in ▁by ▁providing ▁assistance ▁in ▁the ▁process ▁of ▁issu ance ▁and ▁liquid ity ▁to ▁the ▁market ▁and ▁one ▁year ▁later , ▁the ▁SE C ▁adopted ▁its ▁rule ▁ 4 1 5 , ▁which ▁permitted ▁delayed ▁or ▁continuous ▁issu ance ▁of ▁so - called ▁sh elf ▁registered ▁corpor ate ▁se cur ities , ▁en abling ▁issu ers ▁to ▁register ▁se cur ities ▁that ▁may ▁be ▁sold ▁for ▁two ▁years ▁after ▁the ▁effective ▁date ▁of ▁the ▁registration ▁without ▁the ▁need ▁for ▁appro val ▁for ▁each ▁individual ▁offering . ▁Because ▁of ▁these ▁changes , ▁invest ors ▁also ▁become ▁more ▁aware ▁of ▁this ▁instruments ▁and ▁were ▁willing ▁to ▁add ▁it ▁to ▁their ▁port fol ios . ▁This ▁improved ▁liquid ity ▁and ▁helped ▁the ▁growth ▁of ▁the ▁M TM ▁market . ▁In ▁the ▁beg inn ings , ▁most ▁of ▁the ▁issues ▁were ▁fixed ▁rate , ▁non call able ▁and ▁un sec ured ▁deb t ▁of ▁m atur ity ▁shorter ▁than ▁ 5 ▁years . ▁Through out ▁the ▁years , ▁due ▁to ▁specific ▁needs ▁of ▁invest ors ▁and ▁business es , ▁more ▁flexible ▁forms , ▁like ▁notes