U.S.home prices continued their recovery in January, posting the biggest-year-over year increase since 2006, according to one well-known price index.

According to the S&P Case-Shiller index, which tracks the country’s largest metropolitan-area markets, January prices rose by 8.1 percent. According to the index, that is the biggest one-year gain since June 2006, right before the housing “bubble” burst.

All 20 metro areas in the index showed year-over-year price increases, and all but one –Detroit– posted an increase in the rate at which prices were rising.

Rising home prices have been attributed to several factors, including a decreasing number of homes in foreclosure, tight inventories that result in sellers markets in some areas, and declining unemployment.