Year	Percent
1990	11.72
1991	11.43
1992	11.48
1993	11.16
1994	12.39
1995	12.22
1996	12.11
1997	12.2
1998	11.86
1999	12.24
2000	12.84
2001	12.98
2002	13.21
2003	13.98
2004	14.44
2005	15.05
2006	15.4
2007	16.02
2008	16.8
2009	17.19
2010	17.36
2011	17.87
2012	18.46
2013	18.68
2014	18.57
2015	18.92
2016	19.3
2017	19.33
2018	19.55
2019	20.15