| Year | Value | | 2021 | 52.981722387102 | | 2020 | 53.426951151039 | | 2019 | 53.872174540788 | | 2018 | 54.317405951713 | | 2017 | 54.762629341461 | | 2016 | 55.207844710035 | | 2015 | 55.653076120959 | | 2014 | 56.098301114944 | | 2013 | 56.543526108928 | | 2012 | 56.988751102912 | | 2011 | 57.433976096896 | | 2010 | 57.87920109088 | | 2009 | 58.324425282747 | | 2008 | 58.769649474613 | | 2007 | 59.214873666479 | | 2006 | 59.660097858346 | | 2005 | 60.105322050213 | | 2004 | 60.550546242079 | | 2003 | 60.995770433946 | | 2002 | 61.440994625812 | | 2001 | 61.886218817679 | | 2000 | 62.331443009545 | | 1999 | 62.456105719098 | | 1998 | 62.580768428652 | | 1997 | 62.705431138205 | | 1996 | 62.830093847758 | | 1995 | 62.954756557311 | | 1994 | 63.079419266864 | | 1993 | 63.204081976418 | | 1992 | 63.328744685971 | | 1991 | 63.453407395524 | | 1990 | 63.578070105077 |
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