Year	Percent
1975	3.76
1976	3.74
1982	7.59
1983	7.94
1984	6.04
1985	5.75
1986	4.78
1987	4.53
1989	3.11
1990	4.64
1991	7.97
1992	13.71
1993	22.74
1994	22.62
1995	19.61
1996	21.53
1997	21.86
1998	17.5
1999	16.27
2000	9.48
2001	11.67
2002	12.93
2003	14.33
2004	18.54
2005	21.91
2006	21.5
2007	19.27
2008	20.21
2009	25.03
2010	24.78
2011	22.8
2012	23.64
2013	23.54
2014	22.88
2015	20.4
2016	18.93
2017	17.92
2018	17.43
2019	20.13
2020	23.95