Year	Percent
1990	21.16
1991	20.98
1992	19
1993	18.16
1994	17.65
1995	17.21
1996	15.72
1997	15.77
1998	15.32
1999	15.68
2000	15.91
2001	15.96
2002	16.26
2003	16.63
2004	16.29
2005	15.6
2006	14.85
2007	14.13
2008	12.76
2009	11.47
2010	10.79
2011	11.34
2012	11.86
2013	12.23
2014	12.65
2015	13.18
2016	13.29
2017	13.3
2018	13.61
2019	14.51