Year % 1997 18.2094081942337 1998 18.2094081942337 1999 18.361153262519 2000 18.361153262519 2001 17.9059180576631 2002 17.9059180576631 2003 17.9059180576631 2004 18.0576631259484 2005 19.6594427244582 2006 19.6594427244582 2007 19.5046439628483 2008 19.5046439628483 2009 19.5046439628483 2010 22 2011 22.3076923076923 2012 22.4615384615385 2013 22.4615384615385 2014 22.6153846153846 2015 29.3846153846154 2016 29.5839753466872 2017 32 2018 32.1538461538462 2019 32 2020 33.8461538461538 2021 34.2592592592593 2022 34.5679012345679 2023 34.6153846153846