Year	Percent
1970	9.18079
1971	8.79125
1972	8.79786
1973	5.03668
1974	4.2429
1975	5.61348
1976	5.66061
1977	6.85204
1978	7.65198
1979	10.54544
1980	10.35469
1981	11.64958
1982	17.563
1983	16.72574
1984	20.73989
1985	34.94306
1986	33.62691
1987	34.99955
1988	35.43893
1989	40.26017
1990	41.3244
1991	41.43853
1992	40.79986
1993	46.45039
1994	51.55715
1995	51.10441
1996	55.35882
1997	50.91691
1998	57.73234
1999	57.49966
2000	68.08223
2001	57.30222
2002	63.43629
2003	42.64694
2004	37.31212
2005	30.51635
2006	29.30561
2007	27.60674
2008	27.93891
2009	31.45666
2010	25.69958
2011	24.32029
2012	28.06491
2013	31.23388
2014	31.95238
2015	33.97856
2016	35.8646