Their use at public entertainments, charity bazaars and in hospitals made them increasingly familiar however, and in 1906 a charity was set up specifically to ensure even poor children in London slums "who had never seen a Christmas tree" would enjoy one that year. Anti-German sentiment after World WarI briefly reduced their popularity but the effect was short-lived, and by the mid-1920s the use of Christmas trees had spread to all classes. In 1933 a restriction on the importation of foreign trees led to the "rapid growth of a new industry" as the growing of Christmas trees within Britain became commercially viable due to the size of demand. By 2013 the number of trees grown in Britain for the Christmas market was approximately eight million and their display in homes, shops and public spaces a normal part of the Christmas season.