Year	Percent
1981	26.11
1983	25.5
1985	31.64
1986	35.45
1987	44.75
1988	43.43
1989	45.8
1990	42.46
1991	42.28
1993	40.14
1995	35.23
1996	36.02
1998	32.57
1999	30.86
2000	27.65
2002	26.36
2005	21.59
2006	17
2007	14.23
2008	12.86
2009	14.39
2010	9.2995
2011	10.4168
2012	8.3965
2013	6.2861
2014	5.4308
2015	4.6825
2016	6.9368