Year	Percent
1991	37.034
1992	37.121
1993	36.557
1994	35.855
1995	36.084
1996	35.724
1997	34.698
1998	35.143
1999	34.447
2000	34.833
2001	34.58
2002	34.691
2003	34.476
2004	34.753
2005	35.094
2006	35.803
2007	36.176
2008	36.184
2009	35.124
2010	35.51
2011	35.763
2012	35.19
2013	34.489
2014	33.825
2015	32.385
2016	31.631
2017	31.121
2018	30.989
2019	30.863
2020	30.753
2021	30.649
2022	30.544