A philatelist is a person who collects stamps. Collecting stamps has been a popular hobby around the world since the mid-19th century. Philatelists collect stamps of historical significance, with valuations based on the stamp's condition, design, printing method, gum and postage markings.
In addition to collecting stamps, some philatelists also collect envelopes, mailing labels and other accessories related to mail. The American Philatelic Society estimates that around five million people in the United States collect stamps. Stamp collectors value stamps produced with rare errors very highly, with the most valuable stamps exceeding prices of $10 million at auction. An aerophilatelist is a stamp collector who focuses on airmail stamps.