Year | Value | 2022 | 1.8269935498515 | 2021 | 1.8994409948013 | 2020 | 1.9009408139749 | 2019 | 1.8724479121248 | 2018 | 1.9050275814756 | 2017 | 2.0468969747084 | 2016 | 2.1696163026429 | 2015 | 2.1600642726895 | 2014 | 2.1526922059159 | 2013 | 2.1446745489226 | 2012 | 2.1382393591356 | 2011 | 2.1186303279111 | 2010 | 2.0841451872324 | 2009 | 2.0477726290145 | 2008 | 2.0172880272233 | 2007 | 2.0042306267579 | 2006 | 2.0003322857318 | 2005 | 1.9643904110499 | 2004 | 1.915137697063 | 2003 | 1.9630856667318 | 2002 | 2.0431000845572 | 2001 | 2.0255206321345 | 2000 | 1.9404277560748 | 1999 | 2.0115758644685 | 1998 | 2.1403531285296 | 1997 | 2.15054304118 | 1996 | 2.1529427298264 | 1995 | 2.148346693144 | 1994 | 2.1691805649672 | 1993 | 2.2543593199656 | 1992 | 2.3933667566365 | 1991 | 2.5552228535076 | 1990 | 2.7120409841493 | 1989 | 2.7825015925856 | 1988 | 2.7787122905076 | 1987 | 2.7638085657756 | 1986 | 2.7355660937397 | 1985 | 2.6942979850866 | 1984 | 2.6399390680234 | 1983 | 2.5837982248272 | 1982 | 2.6473031528959 | 1981 | 2.8991365789612 | 1980 | 3.1575008269138 | 1979 | 3.2539636439117 | 1978 | 3.2295040429487 | 1977 | 3.1834391121501 | 1976 | 3.0850866124762 | 1975 | 3.0149722275985 | 1974 | 2.9850175068239 | 1973 | 2.9010622421884 | 1972 | 2.8189724983704 | 1971 | 2.7330833036872 | 1970 | 2.6546808980568 | 1969 | 2.5887065548927 | 1968 | 2.4875152263495 | 1967 | 2.23228183348 | 1966 | 2.0400976477717 | 1965 | 2.0085072885985 | 1964 | 1.9746046170793 | 1963 | 1.9649936892427 | 1962 | 1.9494863849797 | 1961 | 1.9138051104114 |
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