Viewership increased exponentially from the 1960s until the end of the 20th century. This was due to the advent of satellites for broadcasting live television worldwide starting in 1964, and the introduction of colour television in 1968.[125] The global audience for the 1968 Mexico City Games was estimated to be 600 million, whereas the audience numbers at the Los Angeles Games of 1984 had increased to 900 million; this number had swelled to 3.5 billion by the 1992 Summer Olympics in Barcelona.[126][127][128][129][130] With such high costs charged to broadcast the Games, the added pressure of the internet, and increased competition from cable, the television lobby demanded concessions from the IOC to boost ratings. The IOC responded by making a number of changes to the Olympic programme; at the Summer Games, the gymnastics competition was expanded from seven to nine nights, and a Champions Gala was added to attract greater interest;[131] the events programmes were also expanded for swimming and diving, both popular sports with a broad base of television viewers.[131] Due to the substantial fees NBC has paid for rights to the Olympics, the IOC has allowed the network to influence the event scheduling to maximise U.S. television ratings when possible.[132][129][133][134]