Global investors were awash in cash due to current account surpluses in emerging economies and easy monetary policies. Investors from emerging economies first invested their rapidly rising wealth in risk-free Treasuries, but once they had their fill of Treasuries they looked for higher yield in what they thought was the next safest thing, U.S. residential mortgages. Due to shrinking returns on less risky investments, other global investors began to search for yield by taking more risk investing in more complicated securities and derivatives.