Year | Value | 2021 | 13.645645081542 | 2020 | 14.096626967801 | 2019 | 14.926132434548 | 2018 | 15.432680340063 | 2017 | 16.186680606905 | 2016 | 16.793707618528 | 2015 | 16.603071754196 | 2014 | 17.345409186992 | 2013 | 17.403824482082 | 2012 | 18.065557730193 | 2011 | 17.800522087901 | 2010 | 17.521970597812 | 2009 | 17.686863284783 | 2008 | 17.860620938951 | 2007 | 17.924790827918 | 2006 | 18.016286275278 | 2005 | 18.307246114527 | 2004 | 18.503561048704 | 2003 | 18.714847232816 | 2002 | 19.094603238339 | 2001 | 19.518877035869 | 2000 | 19.864270110811 | 1999 | 20.2256222303 | 1998 | 20.859533241155 | 1997 | 21.445826588789 | 1996 | 21.903880509455 | 1995 | 22.306789279254 | 1994 | 22.853108479701 | 1993 | 23.310164884153 | 1992 | 23.789668997984 | 1991 | 24.671577524107 | 1990 | 25.439850794379 | 1989 | 26.096330003074 | 1988 | 26.820228308152 | 1987 | 27.536010955327 | 1986 | 27.649677064235 | 1985 | 27.383823857188 | 1984 | 27.348385401811 | 1983 | 27.665202621437 | 1982 | 28.504697052664 | 1981 | 28.204766727231 | 1980 | 27.442930518309 | 1979 | 27.393698166763 | 1978 | 27.649899424758 | 1977 | 28.040112803435 | 1976 | 28.641122411742 | 1975 | 29.855727085356 | 1974 | 30.746177709027 | 1973 | 32.016109160007 | 1972 | 32.810026529878 | 1971 | 33.278389721185 | 1970 | 34.346216164496 | 1969 | 34.758844288913 | 1968 | 35.516200092596 | 1967 | 35.213443890789 | 1966 | 35.795425230345 | 1965 | 37.110283370879 | 1964 | 37.909342826598 | 1963 | 39.709775066848 | 1962 | 37.842692940767 | 1961 | 31.494985480912 | 1960 | 32.669303116656 |
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