Year	Percent
1979	3.1209
1980	3.1783
1981	3.1164
1982	4.3595
1983	6.9302
1984	6.1722
1985	5.6302
1986	5.4841
1987	5.6631
1988	4.758
1989	4.1733
1990	4.874
1991	7.5354
1992	8.7006
1993	9.095
1994	7.8603
1995	6.9518
1996	6.7392
1997	6.6606
1998	6.3327
1999	5.5727
2000	5.1464
2001	5.4064
2002	5.0638
2003	4.5822
2004	3.9576
2005	3.6524
2006	3.44
2007	2.9508
2008	2.9064
2009	4.5106
2010	3.7449
2011	3.5716
2012	3.7954
2013	4.4348
2014	4.5897
2015	4.5612
2016	4.0931
2017	4.0662