Year	Percent
1971	3.26558
1972	4.11136
1973	4.22421
1974	4.39595
1975	4.66373
1976	5.12536
1977	5.91633
1978	7.07094
1979	9.33781
1980	10.55838
1981	10.80791
1982	11.47052
1983	12.50897
1984	13.78738
1985	14.03776
1986	15.5193
1987	16.17921
1989	10.71344
1990	10.96785
1991	12.76537
1992	13.24693
1993	12.6757
1995	9.76597
1996	13.73903
1997	13.49635
1998	14.26171
1999	14.56659
2000	14.54075
2001	15.1236
2002	16.71248
2003	16.65721
2004	20.89501
2005	22.98791
2006	25.49411
2007	30.93397
2008	30.95272
2009	32.84291
2010	33.98835
2011	37.60947
2012	41.60163
2013	42.32049
2014	50.88208
2016	65.33816