Year Number 1970 108700 1971 51000 1972 47900 1973 51600 1974 56500 1975 95000 1976 113700 1977 120400 1978 132200 1979 137300 1980 151100 1981 379100 1982 382300 1983 388500 1984 397700 1985 182700 1986 184900 1987 183400 1988 190700 1989 218200 1990 200200 1991 177700 1992 195100 1993 186200 1994 156900 1995 174700 1996 178700 1997 157600 1998 162400 1999 259600 2000 107979 2001 46364 2010 516085 2011 89791.8677663574 2012 39485.4722019258 2013 234996 2014 237120 2015 642893 2016 667062 2017 808471 2018 825257 2019 748540 2020 322841 2021 569309