In the summer of 2006, the Case-Shiller index of house prices peaked.[52] In California home prices had more than doubled since 2000[53] and median house prices in Los Angeles had risen to ten times the median annual income. To entice the low and moderate income to sign up for mortgages, down payments, income documentation were often dispensed with and interest and principal payments were often deferred upon request.[54] Journalist Michael Lewis gave as an example of unsustainable underwriting practices a loan in Bakersfield, California, where "a Mexican strawberry picker with an income of $14,000 and no English was lent every penny he needed to buy a house of $724,000".[54] As two-year "teaser" mortgage rates - common with those that made home purchases like this possible - expired, mortgage payments skyrocketed. Refinancing to lower mortgage payment was no longer available since it depended on rising home prices.[55] Mezzanine tranches started to lose value in 2007, by mid year AA tranches were worth only 70 cents on the dollar. By October triple-A tranches had started to fall.[56] Regional diversification notwithstanding, the mortgage backed securities turned out to be highly correlated.