Deltiology, the formal name in the U.S. for postcard collecting, is currently the third largest collectable hobby in the world. It is surpassed only by coin and stamp collecting (in the U.S. baseball collecting is greater, but that is a national past-time not worldwide). The popularity of post cards can be attributed to their broad subject appeal. Almost any subject imaginable has been, at some time, portrayed on a postcard. The broad subject range comes as a result of the social usage cards were designed for. Postcards continue today to be the most popular form of souvenir for travelers as well as economical means of communication both personal and business related.
