Question: What year did the stadium where the 1983 FIFA World Youth Championship final was held open in?
Context: The Estadio Azteca (] ) is a football stadium located in the suburb of Santa Úrsula in Mexico City, Mexico.  Since its opening in 1966, the stadium has been the official home stadium of the professional Mexican football team América and the official national stadium of the Mexico national football team.  With an official capacity of 87,000, it is the largest stadium in Mexico.  The stadium sits at an altitude of 7,200 feet above sea level. The 1983 FIFA World Youth Championship, the fourth edition of the FIFA World Youth Championship, was held in Mexico from June 2 to June 19, 1983.  The tournament took place in seven venues — Guadalajara, Irapuato, León, Mexico City, Monterrey, Puebla and Toluca — where a total of 32 matches were played.  The winner was Brazil, who beat Argentina by 1–0, in a final held at Mexico City's Azteca Stadium. The 1979 FIFA World Youth Championship, the second staging of the FIFA World Youth Championship, was held in Japan from August 26 to September 7, 1979.  The tournament took place in four venues — Kobe, Omiya, Tokyo and Yokohama — where a total of 32 matches were played, four more than in the previous edition due to the addition of a quarterfinal round in the knockout stage.  The winner was Argentina, who beat holders Soviet Union by 3–1, in a final held at Tokyo's National Stadium. The 1991 FIFA World Youth Championship was the sixth staging of the FIFA World Youth Championship, an international football competition organized by FIFA for men's youth national teams, and the eighth since it was established in 1977 as the FIFA World Youth Tournament.  The final tournament took place for the first time in Portugal, between 14 and 30 June 1991.  Matches were played across five venues in as many cities: Faro, Braga, Guimarães, Porto and Lisbon. The 1977 FIFA World Youth Championship was the inaugural staging of the FIFA World Youth Championship and was held in Tunisia from 27 June to 10 July 1977.  The tournament took place in three venues — Tunis, Sousse and Sfax — where a total of 28 matches were played, the smallest number in its history.  The winner was USSR, who beat Mexico by a penalty shootout, in a final held at Tunis's Stade El Menzah. The 1985 FIFA World Youth Championship, the fifth edition of the FIFA World Youth Championship, was held in the Soviet Union (USSR) from August 24 to September 7, 1985.  The tournament took place in ten venues within eight host cities — Baku, Yerevan, Leningrad, Minsk (2), Moscow, Hoktemberyan, Tbilisi (2) and Sumqayit — where a total of 32 matches were played.  The winner was Brazil, which managed to retain the title, by beating Spain by 1–0, in the final played at Moscow's Luzhniki Stadium. The South American Youth Championship 1983 was held in Cochabamba, La Paz and Santa Cruz, Bolivia.  It also served as qualification for the 1983 FIFA World Youth Championship. The African Youth Championship 1983 was contested through home and away matches.  It also served as qualification for the 1983 FIFA World Youth Championship. The 1981 FIFA World Youth Championship, the third edition of the FIFA World Youth Championship, was held in Australia from 3 to 18 October 1981.  The tournament took place in six venues—where a total of 32 matches were played.  Adelaide, Brisbane, Canberra, Melbourne, Newcastle and Sydney—The winner was West Germany, who beat surprising Qatar by 4–0, in a final held at Sydney Cricket Ground. Following is a list of the 1993 FIFA World Youth Championship squads.  The FIFA U-20 World Cup, until 2005 known as the FIFA World Youth Championship, is the world championship of football for male players under the age of 20 and is organized by "Fédération Internationale de Football Association" (FIFA).  The Championship has been awarded every two years since the first tournament in 1977 held in Tunisia.
Answer: 1966