Year	Percent
1971	7.19572
1972	6.79262
1973	7.03776
1974	6.79653
1975	7.6261
1976	7.55316
1977	8.55744
1978	8.74263
1979	9.5608
1980	9.32447
1981	10.29991
1982	10.54666
1983	11.30796
1984	12.30674
1985	13.90582
1987	15.82594
1988	16.91584
1989	16.58723
1990	19.4958
1991	19.95185
1992	26.68047
1993	26.24488
1994	27.11621
1995	18.59446
1996	22.57244
1999	23.46804
2000	25.42222
2001	26.67762
2002	27.48547
2003	29.11165
2004	30.42653
2005	31.73658
2006	32.80562
2007	34.97427
2008	38.86926
2009	43.91451
2010	47.05522
2012	57.36603
2013	62.34419
2014	60.84963
2015	62.02993
2016	61.72434