| Year | Value | | 2022 | 2.1674905163412 | | 2021 | 2.0126653708696 | | 2020 | 1.7145817419643 | | 2019 | 1.6093035892758 | | 2018 | 1.5524899195612 | | 2017 | 1.6435928079387 | | 2016 | 1.6003506386231 | | 2015 | 1.7605766855117 | | 2014 | 1.8231815158682 | | 2013 | 1.625009301841 | | 2012 | 1.670357718183 | | 2011 | 1.7515670730985 | | 2010 | 1.6811900440367 | | 2009 | 1.7898210508948 | | 2008 | 1.8317261289334 | | 2007 | 1.6167976254988 | | 2006 | 1.6701188563653 | | 2005 | 1.7456436014363 | | 2004 | 1.7418659209934 | | 2003 | 2.027701043585 | | 2002 | 2.7098436114356 | | 2001 | 2.7046085536652 | | 2000 | 3.0209866026485 | | 1999 | 4.4163769332214 | | 1998 | 5.5952512968371 | | 1997 | 7.5215864238208 | | 1996 | 8.1632147035806 | | 1995 | 9.1756913227081 | | 1994 | 11.148177289424 | | 1993 | 10.726757154505 | | 1992 | 7.6073864434083 |
|