Philately is an irrational pursuit. Serious collectors generally eschew philatelic items that are produced intentionally for their collecting. Thus, many serious collectors ignore First Day Covers, intentionally issued errors and imperfs, Souvenir cards and similar items. But one area that is an exception to this is Souvenir Sheets. Souvenir Sheets were originally issued mostly for philatelic exhibitions and the first souvenir sheet was issued by Luxembourg in 1923. By 1930, many Post Offices were issuing souvenir sheets to commemorate exhibitions and these became avidly collected by collectors. Perhaps this was because the earliest serious collectors were present at these exhibitions where the first souvenir sheets were issued and for sale and purchased them for their collections as souvenirs. Stamp collecting has its “in crowd” aspects just like other human activities. When each new generation of collectors comes into serious collecting they tend to imitate what the “cool guy” older collectors are already collecting. By the 1950s, Souvenir Sheets had made it into serious philately and it was then that many nations began to decouple Souvenir Sheets from philatelic exhibitions and just issue them as parts of sets. This has proved only moderately successful and for many newer collectors, the plethora of Souvenir Sheets combined with their size and difficulty of storage has made Souvenir Sheets comparatively less popular than they have been in the past.