Year | Value | 2023 | 21.387641519037 | 2022 | 24.028275197302 | 2021 | 24.515326583477 | 2020 | 25.053949038699 | 2019 | 23.780933493608 | 2018 | 23.422417893189 | 2017 | 23.202769978889 | 2016 | 21.283287409017 | 2015 | 20.891329267979 | 2014 | 20.690723139559 | 2013 | 20.368265735357 | 2012 | 21.480131362524 | 2011 | 22.899058034058 | 2010 | 23.885413404192 | 2009 | 23.860235657114 | 2008 | 28.269556868992 | 2007 | 30.013595243443 | 2006 | 28.760117079484 | 2005 | 28.603281892907 | 2004 | 29.594919699815 | 2003 | 28.016126403058 | 2002 | 30.9010491458 | 2001 | 31.962966647322 | 2000 | 31.265846181629 | 1999 | 29.16980409515 | 1998 | 27.665432700499 | 1997 | 26.425893585239 | 1996 | 23.290751389531 | 1995 | 23.778610161511 | 1994 | 20.644838007507 | 1993 | 17.672312044274 | 1992 | 16.974307262609 | 1991 | 19.395118909288 | 1990 | 26.680802474716 | 1989 | 28.391356733113 | 1988 | 28.968507777633 | 1987 | 26.677867623516 | 1986 | 27.146918923359 | 1985 | 27.418414012121 | 1984 | 28.332562035286 | 1983 | 27.689432433747 | 1982 | 28.041049161737 | 1981 | 29.36559750327 | 1980 | 30.503528408538 | 1979 | 29.751096329153 | 1978 | 28.161571374916 | 1977 | 27.766154651673 | 1976 | 29.004978679338 | 1975 | 30.641819377875 |
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