Year	Percent
1990	13.97
1991	12.58
1992	12.26
1993	12.49
1994	12.23
1995	12.54
1996	11.41
1997	10.44
1998	10.37
1999	9.86
2000	9.43
2001	10.3
2002	10.43
2003	10.37
2004	10.59
2005	11.27
2006	11.09
2007	10.92
2008	11.79
2009	12.58
2010	13.52
2011	14.5
2012	16.67
2013	17.9
2014	18.51
2015	19.11
2016	21.03
2017	21.14
2018	22.33
2019	22.13