Some stamps were issued in the form of a miniature sheet comprising from one to sixteen stamps of a single, or multiple, design from one issue printed on the same sheet and sold in that format. The miniature sheets are most often produced in addition to the same designs issued as single stamps. The first miniature sheet of four stamp on stamp postage stamps was issued in 1972 to commemorate the 50th anniversary of the first Irish postage stamp. This was followed by a four-stamp sheet to commemorate the bicentenary of the United States Declaration of Independence; the stamps in this sheet were also available as single stamps. A set of four stamps showing Irish wildlife was issued in sheet form and also as single stamps in 1980. Since 1983 miniature sheets have been produced with increasing frequency, from at least one per year initially to several sheets more recently.