The 2008 financial crisis began in the United States and spread around the world due to a complex combination of factors. Subprime mortgage lending became rampant, dragging down the quality of mortgage-backed securities. Regulators and investment banks failed to properly monitor trading and practices in the financial markets. In addition to this, financial institutions leveraged their borrowed capital to an unsustainable degree, hiding high-risk debt off balance sheet. Structured investment vehicles, a form of securitization where subprime mortgages were bundled together and sold to investors, also contributed to the dramatic increase in debt. The global fallout of the crisis was exacerbated by a lack of oversight in the world’s foreign exchange markets, which saw large-scale devaluation of major currencies.