Year	Percent
1974	1.78
1990	4.68
1991	9.22
1992	9.37
1993	8.87
1994	6.46
1995	6.06
1996	5.96
1997	6.46
1998	8.41
1999	8.67
2000	8.73
2001	8.23
2002	8.24
2003	8.42
2004	9.51
2005	8.89
2006	8.19
2007	6.84
2008	5.78
2009	6.92
2010	6.4
2011	5.51
2012	4.79
2013	4.41
2014	4.1
2015	3.92
2016	3.79
2017	3.44
2018	3
2019	2.86
2020	3.08