| Year | Value | | 2022 | 15,318 | | 2021 | 16,450 | | 2020 | 17,418 | | 2019 | 17,813 | | 2018 | 17,730 | | 2017 | 17,559 | | 2016 | 17,255 | | 2015 | 16,893 | | 2014 | 16,548 | | 2013 | 16,200 | | 2012 | 15,804 | | 2011 | 15,430 | | 2010 | 15,222 | | 2009 | 15,051 | | 2008 | 14,880 | | 2007 | 14,900 | | 2006 | 15,025 | | 2005 | 15,053 | | 2004 | 15,095 | | 2003 | 15,149 | | 2002 | 15,067 | | 2001 | 15,041 | | 2000 | 15,136 | | 1999 | 15,153 | | 1998 | 15,037 | | 1997 | 14,767 | | 1996 | 14,414 | | 1995 | 14,027 | | 1994 | 13,542 | | 1993 | 13,043 | | 1992 | 12,678 | | 1991 | 12,410 | | 1990 | 11,986 | | 1989 | 12,013 | | 1988 | 12,274 | | 1987 | 12,697 | | 1986 | 13,210 | | 1985 | 13,714 | | 1984 | 14,166 | | 1983 | 14,683 | | 1982 | 14,908 | | 1981 | 14,882 | | 1980 | 14,857 | | 1979 | 14,648 | | 1978 | 14,440 | | 1977 | 14,141 | | 1976 | 13,904 | | 1975 | 13,741 | | 1974 | 13,708 | | 1973 | 13,885 | | 1972 | 14,083 | | 1971 | 14,281 | | 1970 | 14,364 | | 1969 | 14,288 | | 1968 | 14,103 | | 1967 | 13,739 | | 1966 | 13,125 | | 1965 | 12,341 | | 1964 | 11,482 | | 1963 | 10,687 | | 1962 | 10,166 | | 1961 | 10,003 | | 1960 | 10,122 |
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