Housing affordability, as measured by the Housing Opportunity Index (HOI), dropped from the third to the fourth quarters of 2016 and to its lowest level since 2008, the National Association of Home Builders said.

Shortages of buildable lots and skilled construction laborers, excessive regulations, and rising mortgage rates and home prices made housing less affordable to Americans in the October-to-December time frame, according to the NAHB.

During that period, 59.9 percent of new and existing homes sold were affordable to families earning the national median income of $65,700. This compares to 61.4 percent of homes sold in the third quarter that were deemed affordable to median-income earners.

The national median home price also increased from $247,000 in the third quarter to $250,000 in the fourth quarter, and average mortgage rates moved from 3.76 percent to 3.84 percent from the start of the third quarter to the end of the fourth quarter.