Year	Percent
1978	8.64
1979	8.83
1986	20.31
1987	17.52
1988	14.26
1989	11.7
1990	10.36
1991	8.7
1992	9.67
1993	12.11
1994	14.53
1995	15.98
1996	16.97
1997	14.14
1998	9.5
1999	9.18
2000	8.25
2001	8.96
2002	10.46
2003	13.5
2004	14.05
2005	16.22
2006	16.5
2007	16.73
2008	16.66
2009	20.31
2010	22.75
2011	30.26
2012	37.92
2013	38.1
2014	34.77
2015	31.95
2016	27.95
2017	23.87
2018	20.31
2019	18.27
2020	22.55