Year	Percent
1990	51.78
1991	51.766
1992	51.752
1993	51.738
1994	51.724
1995	51.71
1996	51.738
1997	51.766
1998	51.794
1999	51.822
2000	51.85
2001	52.139
2002	52.427
2003	52.716
2004	53.004
2005	53.292
2006	53.58
2007	50.146
2008	46.71
2009	43.305
2010	39.962
2011	36.71
2012	33.575
2013	30.578
2014	27.737
2015	24.522
2016	22.782
2017	22.599
2018	22.417
2019	22.234
2020	22.052
2021	21.869
2022	21.687
2023	21.504
2024	21.321
2025	21.139
2026	20.956
2027	20.774
2028	20.591
2029	20.408
2030	20.226