There is a direct relationship between declines in wealth and declines in consumption and business investment, which along with government spending, represent the economic engine. Between June 2007 and November 2008, Americans lost an estimated average of more than a quarter of their collective net worth.[citation needed] By early November 2008, a broad U.S. stock index the S&P 500, was down 45% from its 2007 high. Housing prices had dropped 20% from their 2006 peak, with futures markets signaling a 30–35% potential drop. Total home equity in the United States, which was valued at $13 trillion at its peak in 2006, had dropped to $8.8 trillion by mid-2008 and was still falling in late 2008. Total retirement assets, Americans' second-largest household asset, dropped by 22%, from $10.3 trillion in 2006 to $8 trillion in mid-2008. During the same period, savings and investment assets (apart from retirement savings) lost $1.2 trillion and pension assets lost $1.3 trillion. Taken together, these losses total a staggering $8.3 trillion. Since peaking in the second quarter of 2007, household wealth is down $14 trillion.