Year	Percent
1991	33.562
1992	32.904
1993	32.603
1994	32.611
1995	32.851
1996	32.65
1997	32.824
1998	32.597
1999	32.113
2000	32.632
2001	32.076
2002	31.114
2003	30.727
2004	30.72
2005	30.648
2006	30.971
2007	30.754
2008	29.951
2009	28.319
2010	27.721
2011	27.526
2012	27.264
2013	27.716
2014	28.015
2015	27.733
2016	27.728
2017	27.817
2018	27.745
2019	27.565
2020	27.458
2021	27.357
2022	27.268