Year	Percent
1970	19.81373
1971	25.03342
1972	22.99578
1973	34.62513
1974	25.62025
1975	30.12097
1976	35.10757
1977	51.42581
1978	61.01951
1979	57.55388
1980	47.05823
1981	42.62641
1982	40.186
1983	34.40243
1984	30.42901
1985	32.39597
1986	36.3756
1987	37.49115
1988	45.72845
1989	50.70293
1990	46.95832
1991	65.50114
1992	59.66245
1993	54.51577
1994	74.10827
1995	83.51796
1996	75.82864
1997	67.24107
1998	66.45207
1999	60.85518
2000	48.91879
2001	42.83008
2002	42.2321
2003	36.34788
2004	27.41283
2005	17.42163
2006	5.26101
2007	4.61241
2008	3.67932
2009	5.46062
2010	4.51456
2011	3.06452
2012	2.68825
2013	2.55562
2014	2.63969
2015	2.91111
2016	3.58593