Year	Percent
1991	44.223
1992	44.491
1993	48.911
1994	48.578
1995	48.067
1996	47.216
1997	45.303
1998	44.31
1999	42.654
2000	41.698
2001	39.663
2002	40.103
2003	39.146
2004	37.846
2005	38.023
2006	37.316
2007	37.771
2008	41.975
2009	44.005
2010	47.612
2011	50.194
2012	49.129
2013	50.167
2014	53.797
2015	53.34
2016	52.834
2017	53.369
2018	54.09
2019	55.195
2020	56.224
2021	57.293
2022	58.242