Washington, D.C. ? The IRS Criminal Investigation Division completed more than 4,200 investigations in the 2007 budget year, with about one half resulting in conviction for a crime, according to a report issued Thursday.

The Treasury Inspector General for Tax Administration said the criminal division showed improvement in a number of key areas last year despite a decline in special agents. Those included cases initiated, completed, recommended for prosecution and those concluding in convictions.

Inspector General J. Russell George said that refund returns verified as containing false wage information under the IRS’s Questionable Refund Program increased from 84,000 in the 2005 processing year to 211,000 in 2007. The average fraudulent claim in 2007 was $6,479, compared to $3,764 the previous year.