| Year | Value | | 2022 | 2.0498651345644 | | 2021 | 2.0655330728348 | | 2020 | 2.1489371921115 | | 2019 | 2.0144305591072 | | 2018 | 2.0614980896327 | | 2017 | 1.5935113404087 | | 2016 | 1.4500622829144 | | 2015 | 1.0373542769559 | | 2014 | 0.94346003576937 | | 2013 | 0.93894195835335 | | 2012 | 0.9076622429155 | | 2011 | 1.0711481169651 | | 2010 | 1.0835925294035 | | 2009 | 1.3773678411083 | | 2008 | 1.6226413755857 | | 2007 | 1.5503987960449 | | 2006 | 1.7052346401121 | | 2005 | 1.6106219265804 | | 2004 | 1.5956582167076 | | 2003 | 1.6100242749369 | | 2002 | 1.5422082755253 | | 2001 | 1.0415387642766 | | 2000 | 0.88171501160681 | | 1999 | 0.75094082841369 | | 1998 | 0.5878479864961 | | 1997 | 0.58211490874144 | | 1996 | 0.6391446833316 | | 1995 | 0.8056568443875 | | 1994 | 0.83875722696653 | | 1993 | 0.73529540643001 | | 1992 | 0.6529353298881 |
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