| Year | Value | | 2024 | 0.89325752932053 | | 2023 | 0.6603718797525 | | 2022 | 0.68581935202887 | | 2021 | 0.65940419295465 | | 2020 | 0.7176906082587 | | 2019 | 0.50933762829756 | | 2018 | 0.46461154493154 | | 2017 | 0.42484915554015 | | 2016 | 0.4800462724454 | | 2015 | 0.45074282393045 | | 2014 | 0.49532103137281 | | 2013 | 0.48764287589738 | | 2012 | 0.45550205117491 | | 2011 | 0.44738699997213 | | 2010 | 0.43322989920748 | | 2009 | 0.47848879582275 | | 2008 | 0.37317675556547 | | 2007 | 0.38309243197955 | | 2006 | 0.29748341423514 | | 2005 | 0.34040465022647 | | 2004 | 0.34832658301409 | | 2003 | 0.38671435196889 | | 2002 | 0.39131638969932 | | 2001 | 0.40567921044306 | | 2000 | 0.4085181378342 | | 1999 | 0.42026379391102 | | 1998 | 0.40598760491876 | | 1997 | 0.41724386121564 | | 1996 | 0.43569107787377 | | 1995 | 0.4110445453714 | | 1994 | 0.47601147722627 | | 1993 | 0.40044126697579 | | 1992 | 0.46945465573121 | | 1991 | 0.43540230078229 | | 1990 | 0.43308103547403 | | 1989 | 0.51725582937663 | | 1988 | 0.53614537418479 | | 1987 | 0.58034188919146 | | 1986 | 0.6346224630967 | | 1985 | 0.67631313934383 | | 1984 | 0.6598190599279 | | 1983 | 0.52286631398821 | | 1982 | 0.49541941757511 | | 1981 | 0.51330101438058 | | 1980 | 0.41610738255034 | | 1979 | 0.50529747351263 | | 1978 | 0.50483443141953 | | 1977 | 0.53425620505056 | | 1976 | 0.59810357403355 |
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