Year Number 1970 4293500 1971 4830800 1972 5380800 1973 6018800 1974 6572200 1975 7788200 1976 9502900 1977 10807400 1978 11927200 1979 13205700 1980 14837000 1981 15712200 1982 16017600 1983 16043200 1984 14980500 1985 15874800 1986 16257900 1987 16423100 1988 18809400 1989 19924600 1990 17110900 1991 16253700 1992 21066700 1993 16134800 1994 14243900 1995 13230400 1996 13385700 1997 13161200 1998 12828900 1999 13668700 2000 13644350 2001 18495379 2002 16191622 2003 13756737 2004 16934120 2005 17404468 2006 19959287 2007 20199039 2008 22723429 2009 22127432 2010 33183814.054482583 2011 39379075.22660813 2012 38732387.24388399 2013 38896500.17335996 2014 40338413.27323723 2015 39233518 2016 39962744 2017 41551466.05 2018 48929733.440362394 2019 48048008.9975303 2020 18073886.216 2021 25439426.874