Year | Value | 2021 | 22.024480592688 | 2020 | 21.823159929135 | 2019 | 21.46078273474 | 2018 | 21.935899500725 | 2017 | 22.507650185215 | 2016 | 22.209695603157 | 2015 | 23.308906426156 | 2014 | 22.044612659043 | 2013 | 30.25044290546 | 2012 | 30.225881784506 | 2011 | 29.57843453052 | 2010 | 30.188838782413 | 2009 | 30.33660814946 | 2008 | 29.976646803028 | 2007 | 29.843775165083 | 2006 | 29.972620389757 | 2005 | 30.198099532936 | 2004 | 30.306812691255 | 2003 | 29.191496215172 | 2002 | 30.157835400226 | 2001 | 31.345627315188 | 2000 | 32.477049444355 | 1999 | 32.513287163795 | 1998 | 32.320019326784 | 1997 | 28.94090449357 | 1996 | 28.850599624332 | 1995 | 29.287675191446 | 1994 | 29.363531281607 | 1993 | 28.807253287097 | 1992 | 28.727785002167 | 1991 | 28.586909406155 | 1990 | 28.341280161826 | 1989 | 28.005346048259 | 1988 | 27.907816789481 | 1987 | 27.889755815634 | 1986 | 27.380436353128 | 1985 | 26.802485190001 | 1984 | 26.206473053027 | 1983 | 25.6285218899 | 1982 | 25.140875596012 | 1981 | 24.414824447334 | 1980 | 23.399797717093 | 1979 | 22.359485623465 | 1978 | 21.6912295911 | 1977 | 21.077156480277 | 1976 | 20.065741944806 | 1975 | 19.451668833984 | 1974 | 18.667822568993 | 1973 | 18.187400664644 | 1972 | 17.970668978471 | 1971 | 17.753937292299 | 1970 | 17.537205606126 | 1969 | 17.320473919954 | 1968 | 17.103742233781 | 1967 | 17.121803207629 | 1966 | 17.085681259934 | 1965 | 17.085681259934 | 1964 | 17.049559312238 | 1963 | 17.049559312238 | 1962 | 17.013437364543 | 1961 | 17.013437364543 |
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