Year	Percent
1990	20.525
1991	20.07
1992	19.658
1993	19.378
1994	19.139
1995	18.81
1996	18.704
1997	18.598
1998	18.493
1999	18.388
2000	18.284
2001	18.18
2002	16.319
2003	14.614
2004	13.06
2005	13.41
2006	13.41
2007	13.18
2008	14.41
2009	14.585
2010	14.762
2011	14.94
2012	15.82
2013	16.428
2014	17.055
2015	17.7
2016	15.9
2017	15.977
2018	16.054
2019	16.132
2020	16.209
2021	16.286
2022	16.363
2023	16.44
2024	16.518
2025	16.595
2026	16.672
2027	16.749
2028	16.826
2029	16.904
2030	16.981