| Year | Value | | 2021 | 13.83299092559 | | 2020 | 13.694189676451 | | 2019 | 13.553367048177 | | 2018 | 13.413930360297 | | 2017 | 13.273146064697 | | 2016 | 13.154411515665 | | 2015 | 13.039534011589 | | 2014 | 12.929708575784 | | 2013 | 12.820503514439 | | 2012 | 12.710826538266 | | 2011 | 12.600995668901 | | 2010 | 12.491465834301 | | 2009 | 12.441808477161 | | 2008 | 12.386262359761 | | 2007 | 12.331169444142 | | 2006 | 12.275189079952 | | 2005 | 12.21700096782 | | 2004 | 12.160463034643 | | 2003 | 12.108628950298 | | 2002 | 12.05881163911 | | 2001 | 12.006046922667 | | 2000 | 11.951092548877 | | 1999 | 11.885279003688 | | 1998 | 11.778799403071 | | 1997 | 11.710059242703 | | 1996 | 11.659011980725 | | 1995 | 11.607964718747 | | 1994 | 11.55691745677 | | 1993 | 11.505870194792 | | 1992 | 11.454822932814 |
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