Sales of previously owned homes fell at the fastest pace on record last month as the boost from a popular tax credit faded, Reuters reported based industry data released today.

The National Association of Realtors said existing home sales fell 16.7 percent to an annual rate of 5.45 million units in December. Analysts had expected a 5.90 million unit pace.

“The drop in home sales is the payback for the acceleration of sales that occurred with the original first-time home buyers tax credit. … There is an issue as to whether the decline represents a fundamental weakening,” said Pierre Ellis, senior global economist at Decision Economics Inc. in New York.

In Greater Des Moines, both the number of contracts written and closed fell. There were 391 contracts written in December, down from 463 in November and 33 fewer than were written in December 2008, according to the Des Moines Area Association of Realtors. Contracts that closed fell dramatically to 451 in December from 822 in November. The association said 446 contracts closed in December 2008.

The average sale price in Greater Des Moines increased from November to December, but remained below the average sale price in December 2008.

Nationally, sales rose 4.9 percent in 2009 to 5.156 million units for the year, while prices fell 12.4 percent from 2008, “probably the largest annual drop since the Great Depression,” said Lawrence Yun, chief economist for the Realtors association.

The median home price rose 1.5 percent from December 2008 to $178,300. That was the first rise since August 2007 and the largest price rise since May 2006.

Sales fell in all four regions of the country. Sales in the Northeast fell 19.5 percent to a seasonally adjusted 910,000 unit pace. Sales in the Midwest fell 25.8 percent to 1.15 million units.

Sales in the South, the country’s largest region, fell 16.3 percent to 2.01 million units and sales in the West fell 4.8 percent to 1.38 million units.

There were 3.29 million units for sale in December, which represents a 7.2-month supply at the December sales pace, up from the 6.5-month supply in November.