Year	Percent
1983	21.31
1984	23.37
1985	24.99
1986	26.17
1987	25.96
1988	25.2
1989	21.81
1990	19.71
1991	23.1
1992	22.73
1993	25
1994	23.01
1995	18.96
1996	18.12
1997	15.91
1998	11.44
1999	8.56
2000	6.53
2001	6.18
2002	7.82
2003	8.13
2004	8.29
2005	8.56
2006	8.6
2007	9.16
2008	13.47
2009	24.5
2010	28.14
2011	29.59
2012	30.8
2013	26.74
2014	23.42
2015	20.23
2016	16.8
2017	14.41
2018	13.75
2019	12.46
2020	15.26