Year	Percent
1975	9.46322
1976	11.2647
1977	10.9272
1978	15.31712
1979	20.11076
1980	38.65949
1981	52.57582
1982	54.14587
1983	49.93746
1984	37.54969
1985	34.82469
1986	35.44816
1987	38.40197
1988	32.38702
1989	33.22679
1990	35.43795
1991	37.86127
1992	32.07799
1993	33.22314
1994	35.17179
1995	23.11225
1996	26.52597
1997	22.47062
1998	25.66789
1999	26.82012
2000	22.6611
2001	13.28712
2002	13.84583
2003	8.62079
2004	4.97806
2005	3.5228
2006	2.83901
2007	4.39481
2008	9.00088
2009	9.02007
2010	5.86555
2011	5.27418
2012	5.40823
2013	7.98346
2014	7.10825
2015	6.3517