In late 1952, Project Blue Book director, Capt. Edward J. Ruppelt, ordered a study of all the cases in the files for 1947-1952, under a contract with the Battelle Memorial Institute. The data were supplied by the Air Force, while the conclusions were those of the Battelle scientists. The Air Force issued the final report as Project Blue Book Special Report No. 1 4. It was released in 1955, accompanied by an Air Force news release. Although the Air Force stated their own conclusion that there was nothing to warrant interest or concern, this was contrary to the conclusions of the Battelle study. The Battelle scientists had stated that of almost 2,000 reports that were deemed to have sufficient information to permit analysis, 22.8% were judged to be unexplained, and another 31.3% were judged to be doubtfully explained. In total, therefore, 54% of the sightings were said to lack convincing explanations.