Year	Percent
1990	15.96
1991	15.95
1992	16.02
1993	16.05
1994	16.08
1995	16.1
1996	16.16
1997	16.21
1998	16.25
1999	16.32
2000	16.4
2001	16.49
2002	16.58
2003	16.67
2004	16.75
2005	16.82
2006	16.9
2007	16.97
2008	17.02
2009	17.06
2010	17.09
2011	17.13
2012	17.17
2013	17.21
2014	17.23
2015	17.23
2016	15.49
2017	13.92
2018	15.16
2019	13.96