Year	Percent
1978	14.31
1979	21.29
1980	15.96
1982	5.26
1983	1.73
1984	1.8
1985	1.5
1986	2.06
1987	2.21
1988	1.72
1989	2.24
1990	1.75
1991	1.89
1992	2.2
1993	3.1
1994	3.58
1995	4.22
1996	4.49
1997	4.56
1998	4.66
1999	4.9
2000	4.66
2001	4.63
2002	4.16
2003	4.24
2004	4.15
2005	3.51
2006	2.88
2007	2.41
2008	3.11
2009	3.4
2010	3.58
2011	3.84
2012	5.26
2013	5.73
2014	5.48
2015	5.54
2016	5.74
2017	5.78
2018	5.71
2019	5.43
2020	5