Year % gross 1970 3.92844009399414 1971 4.02627992630005 1972 4.06670999526978 1973 4.18142986297607 1974 4.53383016586304 1975 4.53725004196167 1976 4.4894700050354 1977 4.69551992416382 1978 4.74706983566284 1979 4.74256992340088 1981 4.25159978866577 1982 4.23919010162354 1983 4.22997999191284 1985 4.42520999908447 1986 4.44805002212524 1987 4.62093019485474 1988 4.83549976348877 1989 5.07315015792847 1991 5.93824005126953 1992 5.95737981796265 1993 6.00220012664795 1994 5.77855014801025 1995 5.60158014297485 1996 5.40397977828979 1997 6.22690010070801 2010 38.7426300048828 2014 32.8891983032227 2015 28.1546497344971 2016 26.6458396911621 2017 26.6233406066895 2018 27.9907398223877 2019 28.9306697845459 2020 29.2951698303223 2021 26.9020900726318