Year | Value | 2022 | 17.519855165704 | 2021 | 19.541963312112 | 2020 | 15.012135318939 | 2019 | 13.690795444957 | 2018 | 11.393915410746 | 2017 | 13.068848578336 | 2016 | 14.622254967432 | 2015 | 14.305827300187 | 2014 | 15.909027608976 | 2013 | 15.194466372912 | 2012 | 16.209945131667 | 2011 | 17.333216546037 | 2010 | 17.331855792157 | 2009 | 18.321366304633 | 2008 | 21.126802398053 | 2007 | 22.231444171701 | 2006 | 21.417229539399 | 2005 | 13.708609732895 | 2004 | 13.782834874787 | 2003 | 21.734533007546 | 2002 | 21.343176878239 | 2001 | 14.214072822783 | 2000 | 14.368437695826 | 1999 | 13.661916375334 | 1998 | 16.129734327596 | 1997 | 16.664282426643 | 1996 | 17.130077356308 | 1995 | 16.51163227006 | 1994 | 15.648362453387 | 1993 | 16.25052791226 | 1992 | 13.651642792926 | 1991 | 13.561856030419 | 1990 | 16.043375230953 | 1989 | 13.630182387496 | 1987 | 15.197764472427 | 1986 | 14.783385583077 | 1984 | 17.621504071208 | 1983 | 18.53685268061 | 1982 | 18.318270220798 | 1981 | 19.908219350049 | 1980 | 22.958545298159 | 1979 | 25.133789033428 | 1978 | 30.062331377963 | 1977 | 32.453115385755 | 1976 | 34.013529525226 |
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