Year	Percent
1990	16.36
1991	16.385
1992	16.635
1993	16.907
1994	17.152
1995	17.463
1996	17.576
1997	17.857
1998	18.132
1999	18.407
2000	18.611
2001	18.788
2002	18.996
2003	19.188
2004	19.328
2005	19.544
2006	19.717
2007	19.887
2008	19.886
2009	19.58
2010	18.99
2011	18.744
2012	18.5
2013	18.64
2014	18.63
2015	18.62
2016	18.61
2017	18.597
2018	18.584
2019	18.571
2020	18.558
2021	18.545
2022	18.532
2023	18.52
2024	18.507
2025	18.494
2026	18.481
2027	18.468
2028	18.455
2029	18.442
2030	18.429