Year | Value | 2022 | 15.565246533376 | 2021 | 16.261913526983 | 2020 | 14.278139159461 | 2019 | 14.071483893204 | 2018 | 14.468160869224 | 2017 | 13.276866056206 | 2016 | 13.955398002532 | 2015 | 6.8044987251419 | 2014 | 6.0679579164573 | 2013 | 5.0142683933101 | 2012 | 6.4988912901068 | 2011 | 6.5320585126522 | 2010 | 7.1166568042736 | 2009 | 6.6226819727437 | 2008 | 15.404856584242 | 2007 | 16.661897238395 | 2006 | 16.061241399524 | 2005 | 13.872696281728 | 2004 | 11.961343466178 | 2003 | 9.4747419519872 | 2002 | 8.5330972244512 | 2001 | 9.7766461245045 | 2000 | 12.880528148104 | 1999 | 18.486466853888 | 1998 | 16.258584132123 | 1997 | 16.270743314766 | 1996 | 16.480750159988 | 1995 | 23.817877356709 | 1994 | 33.798504765652 | 1993 | 37.156474379098 | 1992 | 15.124583202425 | 1991 | 19.372186723586 | 1990 | 18.991729889095 | 1989 | 14.597318740495 | 1988 | 20.182547072916 | 1987 | 18.257969200643 | 1986 | 21.215273230251 | 1985 | 23.974742552643 | 1984 | 17.944487498238 | 1983 | 20.268833453917 | 1982 | 16.164046276292 | 1981 | 19.679447930436 | 1980 | 17.279653823028 | 1979 | 14.251566688386 | 1978 | 18.193846813677 | 1977 | 25.30817950609 | 1976 | 17.429629072564 | 1975 | 12.257292479644 |
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