Year | Value | 2022 | 13.160023939981 | 2021 | 14.455687244716 | 2020 | 14.854752459358 | 2019 | 13.910161759603 | 2018 | 14.437704237306 | 2017 | 14.251468840807 | 2016 | 15.931417716772 | 2015 | 14.684583175251 | 2014 | 13.559214610585 | 2013 | 13.88912141645 | 2012 | 13.890029121097 | 2011 | 13.850887316095 | 2010 | 15.861784799374 | 2009 | 15.824239893884 | 2008 | 15.259285291924 | 2007 | 17.150268180389 | 2006 | 16.454569722558 | 2005 | 14.180206072762 | 2004 | 14.875463154475 | 2003 | 13.413768065193 | 2002 | 14.346387388016 | 2001 | 16.567797683921 | 2000 | 15.765473524393 | 1999 | 15.745398982049 | 1998 | 17.43923120072 | 1997 | 15.729374236928 | 1996 | 14.13878559666 | 1995 | 15.892266734595 | 1994 | 15.244874897983 | 1993 | 13.097043192269 | 1992 | 14.618672887972 | 1991 | 13.184192033161 | 1990 | 19.357231041762 | 1989 | 18.696605884755 | 1988 | 20.915453870673 | 1987 | 21.418813784252 | 1986 | 23.294692336299 | 1985 | 22.516016487486 | 1984 | 18.711585810949 | 1983 | 15.027511578793 | 1982 | 13.487221632213 | 1981 | 14.323902990017 | 1980 | 12.060931044215 | 1979 | 11.636245041645 | 1978 | 12.866441779075 | 1977 | 16.724115134123 |
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