| Year | Value | | 2020 | 0.3700301862403 | | 2019 | 0.36783337965309 | | 2018 | 0.36074163475598 | | 2017 | 0.38230310434368 | | 2016 | 0.39055626370702 | | 2015 | 0.3981043234567 | | 2014 | 0.40292265036321 | | 2013 | 0.41594876578882 | | 2012 | 0.42022131955786 | | 2011 | 0.39890726302556 | | 2010 | 0.46442178377925 | | 2009 | 0.45408864279156 | | 2008 | 0.42459653775491 | | 2007 | 0.42806460008493 | | 2006 | 0.44615331076987 | | 2005 | 0.46486957386801 | | 2004 | 0.491669641268 | | 2003 | 0.5240757370067 | | 2002 | 0.54072760306268 | | 2001 | 0.55317806064201 | | 2000 | 0.61747287146363 | | 1999 | 0.63769356772361 | | 1998 | 0.6649385972571 | | 1997 | 0.77199329885502 | | 1996 | 0.79505388837694 | | 1995 | 0.83254166580616 | | 1994 | 1.1158289526107 | | 1993 | 0.8739818951289 | | 1992 | 0.89499196916821 | | 1991 | 0.88606438825433 |
|