Year	Percent
1991	55.049
1992	57.887
1993	60.718
1994	62.579
1995	65.085
1996	67.032
1997	69.754
1998	70.838
1999	68.68
2000	68.424
2001	67.813
2002	67.423
2003	68.063
2004	67.65
2005	67.262
2006	67.986
2007	68.616
2008	67.547
2009	67.469
2010	67.122
2011	66.276
2012	66.196
2013	66.43
2014	66.992
2015	67.583
2016	68.079
2017	68.051
2018	68.021
2019	67.99
2020	67.959
2021	67.927
2022	67.895