Year	Percent
1970	4.84499
1971	5.12697
1972	5.92179
1973	9.5517
1974	6.5211
1975	5.18024
1976	3.64645
1977	4.40444
1978	3.99036
1979	8.99478
1980	10.39022
1981	11.71316
1982	9.96247
1983	6.37912
1984	6.59646
1985	5.46938
1986	9.21028
1987	13.5719
1988	14.4246
1989	9.48801
1990	15.42027
1991	10.7469
1992	4.22641
1993	7.7275
1994	11.58908
1995	13.12466
1996	10.04331
1997	13.73019
1998	8.53351
1999	19.21343
2000	16.18977
2001	19.04759
2002	6.69694
2003	17.57853
2004	21.35968
2005	14.19766
2006	24.9828
2007	26.52121
2008	6.34707
2009	12.38055
2010	23.2956
2011	17.81216
2012	19.33073
2013	21.17945
2014	22.32225
2015	23.2147
2016	23.97085
2017	19.64557