| Year | Value | | 2022 | 0.95753454014184 | | 2021 | 0.98686488208469 | | 2020 | 1.002004824396 | | 2019 | 0.89462279176571 | | 2018 | 0.96030876212099 | | 2017 | 1.1003346072361 | | 2016 | 1.3843347942822 | | 2015 | 1.5038984270415 | | 2014 | 1.4551130163334 | | 2013 | 1.4992957985064 | | 2012 | 1.4133307074064 | | 2011 | 1.5528531337699 | | 2010 | 1.4902101058211 | | 2009 | 1.8714869441889 | | 2008 | 1.8248437654995 | | 2007 | 1.9585025326082 | | 2006 | 2.0075974014005 | | 2005 | 2.1739290405425 | | 2004 | 2.2630619684083 | | 2003 | 2.6148067311573 | | 2002 | 2.2191313968994 | | 2001 | 2.0849228116252 | | 2000 | 1.6346755480484 | | 1999 | 2.1014815602931 | | 1998 | 1.6053353480933 | | 1997 | 2.0855586507922 | | 1996 | 2.4005643750098 | | 1995 | 2.7513451070467 | | 1994 | 2.8471152813093 | | 1993 | 2.8752453627885 | | 1992 | 2.986421735841 | | 1991 | 3.1992836209704 | | 1990 | 2.5554034648685 | | 1989 | 2.6237016905343 | | 1988 | 2.4261123741475 | | 1987 | 4.1474995375224 | | 1986 | 3.2237338324441 | | 1985 | 3.4516587065961 | | 1984 | 3.752357008171 | | 1983 | 4.4233717562887 | | 1982 | 5.3676153342176 | | 1981 | 5.7851526565185 | | 1980 | 4.2301343137991 | | 1979 | 3.6705152507324 | | 1978 | 3.7111334002006 | | 1977 | 4.8546691403834 | | 1976 | 3.9807726544419 | | 1975 | 4.7241626365753 | | 1974 | 4.1823431621314 | | 1973 | 3.8722426961491 | | 1972 | 4.9789029535865 | | 1971 | 5.3724430721729 | | 1970 | 5.1652717896695 | | 1969 | 3.9222677839187 | | 1968 | 4.4531633153507 | | 1967 | 4.4970292972751 | | 1966 | 4.7282552218643 | | 1965 | 4.0110497237569 | | 1964 | 3.1635519726395 | | 1963 | 2.4206142634045 | | 1962 | 2.1870409662151 | | 1961 | 2.2329096530402 | | 1960 | 2.6764405046028 |
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