Year	Percent
1990	40.485
1991	39.898
1992	39.253
1993	38.331
1994	38.534
1995	38.783
1996	39.491
1997	39.719
1998	39.71
1999	40.14
2000	40.645
2001	40.978
2002	41.299
2003	41.813
2004	42.414
2005	44.326
2006	46.281
2007	48.009
2008	48.904
2009	50.258
2010	50.014
2011	50.179
2012	50.315
2013	50.39
2014	50.314
2015	50.413
2016	50.225
2017	50.408
2018	50.568
2019	50.682
2020	50.739
2021	50.75
2022	50.707
2023	50.643
2024	50.604
2025	50.623
2026	50.703
2027	50.835
2028	51.02
2029	51.254
2030	51.538