Pair skating, which has never included a compulsory phase like the other figure skating disciplines, did not require a short program until the early 1960s, when the ISU "instituted a short program of required moves" as the first part of pair competitions. The short program for pair skating first appeared at the European Championships in 1963, the World Championships in 1964, and the Olympics in 1968. The arrangement of the specific moves, also unlike compulsory figures for single skaters and the compulsory dance for ice dancers, were up to each pair team. According to writer Ellyn Kestnbaum, the short programs introduced in single men and women competitions in 1973 were modeled after the pair skating short program, and the structure of competitions in both single and pair competitions have been identical since the elimination of compulsory figures in 1990.