| Year | Value | | 2022 | 9.5252662862283 | | 2021 | 4.1862150652357 | | 2020 | 4.4641443723286 | | 2019 | 3.3209062698041 | | 2018 | 3.4944584885618 | | 2017 | 4.9759515055389 | | 2016 | 5.4720226940608 | | 2015 | 3.963943162112 | | 2014 | 4.4053523418529 | | 2013 | 5.5835838070988 | | 2012 | 6.3779786562466 | | 2011 | 6.7913829195262 | | 2010 | 5.5161129870374 | | 2009 | 4.6229477832374 | | 2008 | 11.305109882702 | | 2007 | 7.9051177898873 | | 2006 | 6.9203358070759 | | 2005 | 7.7974978178644 | | 2004 | 4.6350075903937 | | 2003 | 6.5592978291005 | | 2002 | 5.032822757112 | | 2001 | 4.8611646275599 | | 2000 | 4.032467112875 | | 1999 | 5.777368986879 | | 1998 | 8.013755189656 | | 1997 | 8.0840013548604 | | 1996 | 9.3303145853193 | | 1995 | 15.448025835253 | | 1994 | 25.177876224996 | | 1993 | 9.3703441597146 | | 1992 | 10.639302189744 | | 1991 | 14.245844608748 | | 1990 | 8.488646496507 | | 1989 | 8.9299414289403 | | 1988 | 10.219687503977 | | 1987 | 9.0135193146375 | | 1986 | 9.3254619000765 |
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