Year	Percent
1990	21.39
1991	19.77
1992	19.8
1993	19.91
1994	20.07
1995	20.18
1996	20.14
1997	20.13
1998	20.23
1999	20.5
2000	20.82
2001	20.95
2002	21.14
2003	21.41
2004	21.73
2005	22.1
2006	22.3
2007	22.55
2008	22.86
2009	23.26
2010	23.81
2011	24.08
2012	24.13
2013	24.11
2014	24.03
2015	23.92
2016	24.15
2017	24.59
2018	25.58
2019	26.5