Among the useful but boring economic tools is the price index.With its whimsical Christmas Price Index, PNC Wealth Management of Pittsburgh, Pa. introduces a useful instructional device along with a bit of mirth and merriment by annually computing the cost of the items in the song, "The Twelve Days of Christmas." Examination of this index illustrates issues in constructing any price index. Let's review some highlights of the 2010 Christmas Price Index.The Partridge in a Pear Tree increased by a modest 1.3 percent.