| Year | Value | | 2022 | 19,833 | | 2021 | 19,076 | | 2020 | 18,544 | | 2019 | 18,348 | | 2018 | 18,551 | | 2017 | 18,989 | | 2016 | 19,421 | | 2015 | 19,708 | | 2014 | 19,771 | | 2013 | 19,625 | | 2012 | 19,396 | | 2011 | 19,216 | | 2010 | 19,111 | | 2009 | 19,040 | | 2008 | 18,977 | | 2007 | 18,860 | | 2006 | 18,604 | | 2005 | 18,193 | | 2004 | 17,649 | | 2003 | 16,951 | | 2002 | 16,092 | | 2001 | 15,119 | | 2000 | 14,088 | | 1999 | 13,059 | | 1998 | 12,094 | | 1997 | 11,217 | | 1996 | 10,404 | | 1995 | 9,619 | | 1994 | 8,996 | | 1993 | 8,593 | | 1992 | 8,264 | | 1991 | 7,974 | | 1990 | 7,741 | | 1989 | 7,541 | | 1988 | 7,358 | | 1987 | 7,241 | | 1986 | 7,182 | | 1985 | 7,153 | | 1984 | 7,174 | | 1983 | 7,253 | | 1982 | 7,380 | | 1981 | 7,541 | | 1980 | 7,726 | | 1979 | 7,928 | | 1978 | 8,119 | | 1977 | 8,268 | | 1976 | 8,355 | | 1975 | 8,365 | | 1974 | 8,307 | | 1973 | 8,201 | | 1972 | 8,080 | | 1971 | 7,923 | | 1970 | 7,745 | | 1969 | 7,562 | | 1968 | 7,298 | | 1967 | 6,921 | | 1966 | 6,495 | | 1965 | 6,075 | | 1964 | 5,691 | | 1963 | 5,448 | | 1962 | 5,307 | | 1961 | 5,139 | | 1960 | 4,972 |
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