| Year | Value | | 2022 | 0.3231903843869 | | 2021 | 0.33776272178618 | | 2020 | 0.11613936096896 | | 2019 | 0.031987012581296 | | 2018 | 0.023461353152777 | | 2017 | 0.011247907097728 | | 2016 | 0.023142530771156 | | 2015 | 0.056110724488573 | | 2014 | 0.097022011332369 | | 2013 | 0.097599636675676 | | 2012 | 0.084147408002309 | | 2011 | 0.10504177223011 | | 2010 | 0.1832399064251 | | 2009 | 0.21452929589383 | | 2008 | 0.17747586672018 | | 2007 | 0.13811034773105 | | 2006 | 0.12429981279666 | | 2005 | 0.14792926206151 | | 2004 | 0.17721647561581 | | 2003 | 0.39915116880633 | | 2002 | 0.40075077233034 | | 2001 | 0.40236324832229 | | 2000 | 0.027974018699249 | | 1999 | 0.4193256157655 | | 1998 | 0.30529558326197 | | 1997 | 0.24301069784206 | | 1996 | 0.11597143724635 | | 1995 | 0.052816571568282 | | 1994 | 0.1995810934442 | | 1993 | 0.27144006176354 | | 1992 | 0.23214482699309 | | 1991 | 0.12080988583242 | | 1990 | 0.032812754067676 | | 1989 | 0.1387168422347 | | 1988 | 0.12027409461196 | | 1987 | 0.071225601458302 | | 1986 | 0.38133470329471 | | 1985 | 0.74841887224285 | | 1984 | 1.0671095664182 | | 1983 | 1.2704285190467 | | 1982 | 1.2955774533193 | | 1981 | 1.1869384945834 | | 1980 | 1.0039610573367 | | 1979 | 0.85442517829961 | | 1978 | 0.80186846556567 | | 1977 | 0.90331726225114 | | 1976 | 1.1055124697104 | | 1975 | 1.3976783397246 | | 1974 | 1.6241721438282 | | 1973 | 1.6036389114758 | | 1972 | 1.221726015508 | | 1971 | 0.59191343566787 | | 1970 | 0.18191625367701 | | 1969 | 0.80344158214458 | | 1968 | -1.0218521121719 | | 1967 | 0.69061429732643 | | 1966 | 0.017478100175005 | | 1965 | 0.872839676191 | | 1964 | 1.6121497346718 | | 1963 | 2.1361742316178 | | 1962 | 2.2981836623194 | | 1961 | 2.1737592567977 |
|