Before 2008 Asset Backed Commercial Paper (ABCP) was central to the shadow banking system. ABCP was issued by special purpose vehicles (SPV's), which held a pool of longer term asset backed loans. After 2008, most of the SPV's that issued the ABCP went into run-off mode, hence the decline of the shadow banking system. Today, that process is surprisingly almost complete for the ABCP market. The amount of ABCP left outstanding has fallen by $1T since 2007, about $200B per year. At that pace, there's about 1.5 year's worth of ABCP supply left.