The number of multi-family property sales doubled from 101 in December 2007 to 202 in December 2008 according to sales statistics released today by the Rhode Island Association of Realtors (RIAR). The percentage of multi-family sales has been increasing throughout the year, up 33.2% in 2008 overall, (1254 in 2007 to 1670 last year) and up 92.9% in the fourth quarter from 281 to 542.