Year	Percent
1990	15.304
1991	15.373
1992	15.435
1993	15.445
1994	15.441
1995	15.501
1996	15.332
1997	15.185
1998	15.093
1999	15.05
2000	15.025
2001	15.344
2002	15.72
2003	16.09
2004	16.417
2005	16.691
2006	16.218
2007	15.768
2008	15.41
2009	15.223
2010	15.243
2011	15.823
2012	16.597
2013	17.513
2014	18.49
2015	19.469
2016	20.211
2017	20.268
2018	20.322
2019	20.373
2020	20.421
2021	20.47
2022	20.515
2023	20.556
2024	20.593
2025	20.628
2026	20.662
2027	20.694
2028	20.722
2029	20.747
2030	20.77