Year	Percent
1990	22
1991	21.65
1992	20.55
1993	20.63
1994	20.49
1995	20.51
1996	19.48
1997	18.75
1998	17.84
1999	16.93
2000	16.03
2001	15.1
2002	14.19
2003	13.32
2004	12.5
2005	11.72
2006	12.79
2007	11.39
2008	9.77
2009	9.39
2010	10.53
2011	9.16
2012	8.06
2013	6.63
2014	6.7
2015	6.82
2016	6.8
2017	6.73
2018	6.61
2019	6.61