Year Number 1970 8038900 1971 8182100 1972 8165700 1973 8291400 1974 7726700 1975 7593200 1976 7809500 1977 8180100 1978 8393500 1979 8715300 1980 8680900 1981 8225900 1982 8201700 1983 8473300 1984 8979200 1985 9477100 1986 10216600 1987 10689900 1988 11260300 1989 11381300 1990 11887100 1991 11657800 1992 12051800 1993 12972400 1994 13970700 1995 14617500 1996 15313900 1997 15710500 1998 15725900 1999 16716800.000976562 2000 18011576 2001 17814539 2002 16512187 2003 17075406 2004 18940544 2005 19089737 2006 19240949 2007 19868002 2008 19310218 2009 19491081 2010 21840425.54736362 2011 22182070.189451274 2012 21922264.967187803 2013 21969443.973863408 2014 22045256.90702441 2015 22416124 2016 22988405 2017 23210633.92 2018 23547850.20835469 2019 23991370.588128358 2020 12186274.697999997 2021 15230929.136