| Year | Value | | 2022 | 1.380786316534 | | 2021 | 2.7775503803674 | | 2020 | 1.5727091461017 | | 2019 | 1.2874876089545 | | 2018 | 1.3144183928328 | | 2017 | 1.4133429727953 | | 2016 | 1.4711446899842 | | 2015 | 1.2783460007428 | | 2014 | 2.2275617200694 | | 2013 | 1.0365589326699 | | 2012 | 0.93667958464137 | | 2011 | 0.85550406331746 | | 2010 | 0.73791536327045 | | 2009 | 1.0208783356142 | | 2008 | 1.1501931969598 | | 2007 | 1.4682835893556 | | 2006 | 1.4134300233089 | | 2005 | 1.6023523510766 | | 2004 | 1.8976402274237 | | 2003 | 1.7343163749902 | | 2002 | 1.6773754709083 | | 2001 | 1.7782655216878 | | 2000 | 1.6793328209945 | | 1999 | 1.7829254421204 | | 1998 | 1.7329155876813 | | 1997 | 2.024810037109 | | 1996 | 2.0957485101788 | | 1995 | 2.2811802628316 | | 1994 | 2.4436854517362 | | 1993 | 2.7596134073617 | | 1992 | 4.7273873306019 | | 1991 | 4.4240189889399 | | 1990 | 4.0262315083117 | | 1989 | 4.27683189029 | | 1988 | 4.2803848419399 | | 1987 | 4.541872626979 | | 1986 | 4.6744186046512 | | 1985 | 4.2908125155615 |
|