Year	Percent
1991	37.451
1992	37.309
1993	37.078
1994	36.644
1995	35.967
1996	35.039
1997	34.111
1998	33.403
1999	32.998
2000	32.774
2001	32.321
2002	32.011
2003	31.997
2004	32.189
2005	32.357
2006	31.649
2007	31.055
2008	30.772
2009	30.712
2010	30.615
2011	29.904
2012	29.214
2013	28.807
2014	28.658
2015	28.513
2016	27.452
2017	26.605
2018	26.104
2019	25.936
2020	25.839
2021	25.094
2022	24.381