Year Number 1970 112500 1971 101100 1972 98000 1973 43000 1974 88800 1975 113500 1976 119000 1977 137800 1978 136300 1979 156300 1980 118900 1981 124400 1982 114600 1983 99500 1984 124000 1985 108400 1986 103100 1987 114800 1988 98900 1989 110200 1990 156000 1991 165000 1992 230000 1993 240000 1994 252000 1995 300000 1996 300000 1997 508400 1998 506400 2010 313892 2011 326146.206150004 2012 288013.900825685 2013 78264 2014 69768 2015 93129 2016 111830 2017 155524 2018 145795 2019 107350 2020 25217.454 2021 1766.181