Year	Percent
1971	19.90111
1972	22.77441
1973	23.67148
1974	15.99413
1975	14.24317
1976	15.41515
1977	11.25594
1978	3.72878
1979	9.07746
1980	2.8383
1981	4.34947
1982	5.63532
1987	1.3998
1988	1.88495
1989	1.65986
1990	1.50802
1991	1.52305
1992	2.53151
1993	0.50526
1994	1.17677
1995	1.34075
1996	3.28559
1997	6.04759
1998	5.56042
1999	8.0206
2000	7.21862
2001	6.01315
2002	7.03885
2003	7.41775
2004	13.12779
2005	14.55609
2006	22.04039
2007	26.86915
2008	24.21434
2009	26.6969
2010	25.69986
2011	23.81457
2012	34.10212
2013	20.51979
2014	22.43541
2015	23.63046
2016	22.27088