Even with the rapid appreciation seen across the country over the past few years, home prices are still quite a bit lower than levels recorded a decade ago. And despite mortgage rates that are already rising, affordability is improving nationwide, but not everywhere – especially in some of the high-end markets in California.

First American’s latest Real Housing Price Index (RHPI) says that as of September, U.S. single-family home prices were 40.4 percent lower than during the height of the last real estate boom in 2006 and 19.9 percent lower than during the dot-com era. The index measures home price changes over time using home prices adjusted for income and interest-rate fluctuations to determine homebuying power and affordability.

Although interest rates ticked above 4 percent for the first time in 2016 last week, nationwide affordability is at its highest level in 25 years.

“Even with the recent uptick in mortgage rates, mortgage rates remain at historically low levels,” First American Chief Economist Mark Fleming said in a statement. “Even as interest rates increase above 4 percent post-election, housing, on a purchasing-power adjusted basis, will continue to be more affordable than it was in the early 1990s.”

Income growth is offsetting both interest-rate increases and home price appreciation to improve affordability conditions, even in the nation’s most expensive real estate markets

 “Affordability continues to increase in more markets than it is decreasing, including markets considered by many to be over-valued, like San Francisco, San Jose, New York, Washington, and Boston,” Fleming said. “Conventional wisdom overlooks the impact that rising incomes can have on consumer house-buying power in a low-rate environment.”