| Year | Value | | 2022 | 0.2582233758869 | | 2021 | 0.34255372370417 | | 2020 | 0.4741169903602 | | 2019 | 0.56657580249464 | | 2018 | 0.65382328261234 | | 2017 | 0.76246963255625 | | 2016 | 0.7520476640732 | | 2015 | 0.76160022975967 | | 2014 | 0.80257034451519 | | 2013 | 0.83968455428614 | | 2012 | 0.85655646696206 | | 2011 | 0.76584238400331 | | 2010 | 0.72350400862595 | | 2009 | 0.73548012760789 | | 2008 | 0.75074627260752 | | 2007 | 0.76291393161982 | | 2006 | 0.78730005383558 | | 2005 | 0.80925877376517 | | 2004 | 0.82093910517096 | | 2003 | 0.85210271176688 | | 2002 | 0.89259223848448 | | 2001 | 0.94085087106359 | | 2000 | 1.0001526547598 | | 1999 | 1.0802474638262 | | 1998 | 1.1690588795362 | | 1997 | 1.2291382847979 | | 1996 | 1.2546060458044 | | 1995 | 1.2928796770882 | | 1994 | 1.3441508089851 | | 1993 | 1.3760162923304 | | 1992 | 1.4360816709787 | | 1991 | 1.5404609614735 | | 1990 | 1.6238936168358 | | 1989 | 1.6776626985515 | | 1988 | 1.7433716463789 | | 1987 | 1.7509116210932 | | 1986 | 1.6805841704258 | | 1985 | 1.6060011048767 | | 1984 | 1.5862690103704 | | 1983 | 1.6898637410758 | | 1982 | 1.7124162729451 | | 1981 | 1.5734120650281 | | 1980 | 1.547421349203 | | 1979 | 1.6060519621006 | | 1978 | 1.6143166467692 | | 1977 | 1.6162464989358 | | 1976 | 1.7388021081147 | | 1975 | 1.9184594903401 | | 1974 | 2.1696338829463 | | 1973 | 2.353425118148 | | 1972 | 2.4971921835201 | | 1971 | 2.718473259212 | | 1970 | 2.7358138195658 | | 1969 | 2.7291934275644 | | 1968 | 2.6338868879928 | | 1967 | 2.6007250359717 | | 1966 | 2.745825060253 | | 1965 | 2.463959613402 | | 1964 | 2.4565946382227 | | 1963 | 2.5615347388744 | | 1962 | 1.3244176982311 | | 1961 | 0.052427416946202 |
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