| Year | Value | | 2024 | 81.429947794484 | | 2023 | 80.899394959346 | | 2022 | 81.689722713909 | | 2021 | 79.730472738076 | | 2020 | 78.351564352465 | | 2019 | 78.229980369651 | | 2018 | 78.647307726246 | | 2017 | 79.451368058802 | | 2016 | 80.504255858113 | | 2015 | 81.050500268608 | | 2014 | 82.562300108031 | | 2013 | 82.460611532602 | | 2012 | 80.611674671005 | | 2011 | 81.230742855332 | | 2010 | 81.816910488851 | | 2009 | 80.502670622329 | | 2008 | 80.533936587067 | | 2007 | 79.270857263735 | | 2006 | 79.166423678339 | | 2005 | 81.302973578192 | | 2004 | 79.935058604458 | | 2003 | 81.147553944189 | | 2002 | 79.497337299636 | | 2001 | 78.612315002928 | | 2000 | 78.046206533621 | | 1999 | 76.442110727965 | | 1998 | 76.100603167192 | | 1997 | 76.732152182715 | | 1996 | 76.512969680147 | | 1995 | 76.840980824474 | | 1994 | 79.214639123421 | | 1993 | 79.651394752174 | | 1992 | 81.843777674908 | | 1991 | 79.912176311238 | | 1990 | 78.397537653373 | | 1989 | 77.67100733288 | | 1988 | 76.690910270971 | | 1987 | 70.946485217093 | | 1986 | 74.609780692618 | | 1985 | 69.685998737756 | | 1984 | 68.926952837114 | | 1983 | 66.41226403823 | | 1982 | 67.825369804417 | | 1981 | 71.202077159767 | | 1980 | 71.160733152629 | | 1979 | 75.299706649283 | | 1978 | 76.980329482242 | | 1977 | 77.071600865333 | | 1976 | 79.086542669584 |
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