Year Number 1960 21977 1961 22785 1962 23625 1963 24419 1964 25161 1965 25935 1966 26737 1967 27541 1968 28360 1969 29213 1970 30099 1971 30951 1972 31759 1973 32583 1974 33425 1975 34197 1976 34903 1977 35640 1978 36545 1979 37615 1980 38716 1981 39841 1982 40991 1983 42170 1984 43377 1985 44599 1986 45827 1987 47064 1988 48148 1989 49069 1990 49988 1991 50917 1992 52223 1993 53918 1994 55407 1995 56122 1996 56257 1997 56325 1998 56334 1999 56279 2000 56309 2001 56446 2002 56495 2003 56421 2004 56246 2005 55995 2006 55656 2007 55253 2008 54828 2009 54393 2010 54246 2011 54398 2012 54568 2013 54755 2014 54957 2015 55166 2016 55388 2017 55630 2018 55865 2019 56072 2020 56413 2021 56898 2022 57387 2023 57891