Year	Percent
1979	5.2899
1980	5.0521
1981	5.0036
1982	5.9275
1983	7.6385
1984	6.8656
1985	6.4039
1986	6.4078
1987	6.4146
1988	6.0059
1989	5.1942
1990	5.3896
1991	7.0033
1992	7.6921
1993	7.9615
1994	7.3257
1995	6.2078
1996	6.445
1997	6.4333
1998	5.7957
1999	5.3064
2000	4.9126
2001	5.1767
2002	5.0061
2003	4.8736
2004	4.3622
2005	4.1153
2006	3.9885
2007	3.9052
2008	3.9109
2009	4.5654
2010	4.3955
2011	4.369
2012	4.3567
2013	4.6982
2014	5.134
2015	5.2281
2016	4.9674
2017	4.7996