| Year | Value | | 2024 | 559 | | 2023 | 549 | | 2022 | 534 | | 2021 | 516 | | 2020 | 497 | | 2019 | 481 | | 2018 | 468 | | 2017 | 456 | | 2016 | 445 | | 2015 | 430 | | 2014 | 411 | | 2013 | 398 | | 2012 | 382 | | 2011 | 359 | | 2010 | 336 | | 2009 | 313 | | 2008 | 292 | | 2007 | 279 | | 2006 | 269 | | 2005 | 255 | | 2004 | 250 | | 2003 | 248 | | 2002 | 246 | | 2001 | 246 | | 2000 | 240 | | 1999 | 222 | | 1998 | 202 | | 1997 | 181 | | 1996 | 167 | | 1995 | 169 | | 1994 | 177 | | 1993 | 186 | | 1992 | 192 | | 1991 | 199 | | 1990 | 208 | | 1989 | 205 | | 1988 | 196 | | 1987 | 192 | | 1986 | 182 | | 1985 | 174 | | 1984 | 175 | | 1983 | 169 | | 1982 | 157 | | 1981 | 147 | | 1980 | 145 | | 1979 | 152 | | 1978 | 160 | | 1977 | 164 | | 1976 | 158 | | 1975 | 139 |
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