| Year | Value | | 2022 | 1.247087134113 | | 2021 | 1.5790225762762 | | 2020 | 1.4971441746167 | | 2019 | 1.729341401051 | | 2018 | 2.0503980197707 | | 2017 | 2.1195481819038 | | 2016 | 2.2280118856987 | | 2015 | 2.2147797948258 | | 2014 | 2.2742960467295 | | 2013 | 2.3655185689657 | | 2012 | 1.5535604589829 | | 2011 | 0.4092775153753 | | 2010 | 0.078147898868201 | | 2009 | 0.097675334977918 | | 2008 | 0.23403228624301 | | 2007 | 0.26263329137352 | | 2006 | 0.23287415918953 | | 2005 | 0.16462503112736 | | 2004 | 0.087044833582467 | | 2003 | 0.067649193205688 | | 2002 | 0.11586368004671 | | 2001 | 0.13500484210611 | | 2000 | 0.057803469817539 | | 1999 | 0.057803469817538 | | 1998 | 0.1350048421061 | | 1997 | 0.1738459004574 | | 1996 | 0.28072231784079 | | 1995 | 0.40796559740223 | | 1994 | 0.46829353872685 | | 1993 | 0.95308999531475 | | 1992 | 2.2665839765429 | | 1991 | 3.1182013503177 | | 1990 | 3.0895390013597 | | 1989 | 3.0993314436253 | | 1988 | 2.9584295805252 | | 1987 | 2.6844143421039 | | 1986 | 2.5417045210961 | | 1985 | 2.287482633315 | | 1984 | 3.6727822987592 | | 1983 | 2.0640567647072 | | 1982 | 0.24734764937797 | | 1981 | 0.7307875404321 | | 1980 | 0.64384954038885 | | 1979 | 0.59496440461972 | | 1978 | 1.3349550805386 | | 1977 | 1.8309320042033 | | 1976 | 1.4753800885925 | | 1975 | 1.4410882479887 | | 1974 | 1.505068876156 | | 1973 | 1.5425952829492 | | 1972 | 1.5372530231368 | | 1971 | 1.7112239604459 | | 1970 | 2.3537644223609 | | 1969 | 3.4389134229886 | | 1968 | 2.8061831658263 | | 1967 | 1.5327864986332 | | 1966 | 3.6706023460369 | | 1965 | 5.6712573321874 | | 1964 | 5.3560825480769 | | 1963 | 4.88863596387 | | 1962 | 4.0611578948727 | | 1961 | 3.6640413600569 |
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