Year Number 1970 3070800 1971 3354500 1972 3415000 1973 3636500 1974 4026800 1975 4387200 1976 5101500 1977 5193400 1978 5664300 1979 6468300 1980 6969100 1981 7255200 1982 7394400 1983 7618200 1984 7991800 1985 7460400 1986 7178000 1987 7293000 1988 7551600 1989 7301700 1990 7434000 1991 6618700 1992 6719700 1993 6433300 1994 6139600 1995 6114500 1996 6751600 1997 6925200 1998 6968200 1999 6849500 2000 6492929 2001 5967306 2010 14165092.226547282 2011 17296028.46343348 2012 18073364.030062713 2013 18079383.818 2014 19361000.320880286 2015 20661772 2016 20915140 2017 23844385.43 2018 26411525.914388243 2019 27353506.86733741 2020 12330289.393000001 2021 19149959.027999997