| Year | Value | | 2022 | 1.6403100659383 | | 2021 | 1.7685782159067 | | 2020 | 1.4169679999008 | | 2019 | 1.0455354418018 | | 2018 | 0.99250570918373 | | 2017 | 1.0097526582137 | | 2016 | 0.96452845576806 | | 2015 | 0.89508354274683 | | 2014 | 0.90516829285184 | | 2013 | 0.91192227258817 | | 2012 | 0.89892233428763 | | 2011 | 0.85877829122258 | | 2010 | 0.77144005855509 | | 2009 | 0.72163092436926 | | 2008 | 0.68486788823699 | | 2007 | 0.57864041807038 | | 2006 | 0.39840795546279 | | 2005 | 0.29360332639678 | | 2004 | 0.33713911346402 | | 2003 | 0.43307470045021 | | 2002 | 0.59114531562518 | | 2001 | 0.82373591140834 | | 2000 | 0.98138787049885 | | 1999 | 1.0071900606983 | | 1998 | 1.0263987045364 | | 1997 | 1.0302520923598 | | 1996 | 1.030113057882 | | 1995 | 1.0315916647853 | | 1994 | 1.0131622450568 | | 1993 | 0.91628933881324 | | 1992 | 0.64874673617671 | | 1991 | 0.30574073868909 | | 1990 | 0.17853321888481 | | 1989 | 0.2588434608165 | | 1988 | 0.40631367141209 | | 1987 | 0.24494365937907 | | 1986 | 0.091323658572112 | | 1985 | 0.15721764075553 | | 1984 | 0.098884412189101 | | 1983 | 0.035347438727206 | | 1982 | 0.41732403132784 | | 1981 | 0.77621616266499 | | 1980 | 0.86238407262212 | | 1979 | 0.92234513718705 | | 1978 | 1.0088498780019 | | 1977 | 1.3978337355043 | | 1976 | 1.8334969061873 | | 1975 | 1.9662230229861 | | 1974 | 1.7580059619124 | | 1973 | 1.5189619773887 | | 1972 | 1.5513519243159 | | 1971 | 1.5933076302519 | | 1970 | 1.6340555940273 | | 1969 | 1.6532387123198 | | 1968 | 1.7539313315209 | | 1967 | 2.0661030859854 | | 1966 | 2.4258605894518 | | 1965 | 2.5019735409411 | | 1964 | 2.5329556797103 | | 1963 | 2.6711608294425 | | 1962 | 2.821486580305 | | 1961 | 3.0286253895843 |
|