Year	Percent
1990	57.536
1991	57.489
1992	57.434
1993	54.969
1994	52.702
1995	50.386
1996	49.588
1997	48.574
1998	50.411
1999	51.674
2000	52.018
2001	51.917
2002	52.311
2003	53.585
2004	53.484
2005	54.832
2006	55.267
2007	54.854
2008	54.661
2009	54.88
2010	56.161
2011	56.486
2012	57.835
2013	58.218
2014	60.316
2015	61.892
2016	63.263
2017	63.736
2018	64.266
2019	64.802
2020	65.305
2021	65.766
2022	66.188
2023	66.563
2024	66.883
2025	67.145
2026	67.334
2027	67.457
2028	67.527
2029	67.563
2030	67.578