Year	Percent
1976	1.5871
1977	1.4446
1978	2.2259
1979	2.1665
1980	1.109
1981	1.4974
1982	2.5672
1983	1.9796
1984	1.2997
1985	1.3645
1986	2.2465
1987	3.6716
1988	2.7894
1989	1.6465
1990	1.5741
1991	5.0151
1992	6.0171
1993	4.7627
1994	6.0718
1995	5.1399
1996	4.3065
1997	3.3445
1998	2.8972
1999	2.1244
2000	2.9115
2001	4.2183
2002	3.419
2003	3.1782
2004	3.3859
2005	3.8023
2006	4.0643
2007	3.3645
2008	2.8978
2009	3.7463
2010	4.4291
2011	4.4949
2012	4.3592
2013	3.752
2014	3.0205
2015	4.1497
2016	3.347
2017	4.6922