Year	Percent
1981	18.04
1983	19.22
1985	28.93
1986	31.2
1987	37.55
1988	37.4
1989	36.88
1990	33.06
1991	29.34
1993	29.56
1995	28.35
1996	23.54
1998	23.32
1999	21.86
2000	20.33
2002	17.44
2005	12.9
2006	10.04
2007	9.35
2008	8.78
2009	9.97
2010	7.8244
2011	6.2054
2012	5.9756
2013	4.2062
2014	3.5384
2015	4.3673
2016	7.1754