Year	Percent
1990	21.2
1991	20.8
1992	18.2
1993	16.8
1994	15.4
1995	15.2
1996	13.5
1997	11.8
1998	11.1
1999	10.898
2000	10.7
2001	10.1
2002	9.7
2003	9.6
2004	9.6
2005	9.7
2006	10.2
2007	9.631
2008	9.09
2009	9.36
2010	9.8
2011	10
2012	11.517
2013	13.23
2014	14.2
2015	14.91
2016	15.59
2017	15.719
2018	15.848
2019	15.977
2020	16.106
2021	16.235
2022	16.364
2023	16.493
2024	16.622
2025	16.751
2026	16.88
2027	17.009
2028	17.138
2029	17.267
2030	17.396