The repeal enabled commercial lenders such as Citigroup, which was in 1999 the largest U.S. bank by assets, to underwrite and trade instruments such as mortgage-backed securities and collateralized debt obligations and establish so-called structured investment vehicles, or SIVs, that bought those securities.[15] Elizabeth Warren,[16] author and one of the five outside experts who constitute the Congressional Oversight Panel of the Troubled Asset Relief Program, has said that the repeal of this act contributed to the Global financial crisis of 2008–2009.[17] [18]