Year	Percent
1971	11.20544
1972	15.95458
1973	16.40165
1974	12.76882
1975	21.59528
1976	29.65049
1977	21.74519
1978	18.30938
1979	16.91436
1980	10.1261
1981	5.94331
1982	6.13488
1983	5.35061
1984	5.528
1985	3.88765
1986	3.79343
1987	3.32606
1988	1.65088
1989	0.7879
1990	1.22027
1991	3.22455
1992	5.1528
1993	2.3805
1994	3.73953
1995	5.49342
1996	5.34923
1997	11.86698
1998	16.16372
1999	22.63816
2000	23.49179
2001	27.5579
2002	27.88749
2003	25.4371
2004	31.90303
2005	45.22408
2006	66.25592
2007	84.86811
2008	71.42208
2009	55.43758
2010	67.91833
2011	63.43767
2012	50.08573
2013	44.04036
2014	47.18779
2015	49.49442
2016	50.31503