| Year | Value | | 2024 | 10.655687712611 | | 2023 | 10.978155320388 | | 2022 | 10.961883544922 | | 2021 | 10.823795184676 | | 2020 | 11.069688503478 | | 2019 | 11.338184714288 | | 2018 | 11.834425042383 | | 2017 | 11.967952728271 | | 2016 | 11.897904141822 | | 2015 | 12.783289202746 | | 2014 | 16.397514925557 | | 2013 | 21.47816316153 | | 2012 | 26.221131976568 | | 2011 | 28.997127647167 | | 2010 | 30.652874605851 | | 2009 | 32.159856782878 | | 2008 | 33.486349109623 | | 2007 | 34.661038184531 | | 2006 | 35.712610606046 | | 2005 | 36.669752972613 | | 2004 | 37.561151882674 | | 2003 | 38.415493934674 | | 2002 | 39.261465727058 | | 2001 | 40.127753858268 | | 2000 | 41.02938799936 | | 1999 | 41.902723364266 | | 1998 | 42.709814268548 | | 1997 | 43.473333024379 | | 1996 | 44.209556113999 | | 1995 | 44.934760019646 | | 1994 | 45.665221223561 | | 1993 | 46.417216207984 | | 1992 | 47.207021455154 | | 1991 | 48.05091344731 | | 1990 | 48.968603965208 | | 1989 | 49.970241671778 | | 1988 | 51.04399304764 | | 1987 | 52.159727961189 | | 1986 | 53.289835764769 | | 1985 | 54.417165518295 | | 1984 | 55.577844939296 | | 1983 | 56.773612147103 | | 1982 | 57.957001264178 | | 1981 | 59.085544918821 | | 1980 | 60.115877993596 | | 1979 | 61.049678057388 | | 1978 | 61.921734368677 | | 1977 | 62.775511027432 | | 1976 | 63.652676576711 |
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