Year	Percent
1971	26.55972
1972	26.63546
1973	26.77717
1978	30.96678
1979	32.49368
1980	30.35248
1981	31.91755
1982	32.2483
1983	33.49224
1984	34.35298
1985	34.46184
1986	37.10292
1988	42.26162
1989	43.09467
1990	42.55972
1992	39.50829
1994	38.26032
1996	39.46135
1997	39.79696
1998	42.23113
1999	41.93204
2000	38.63548
2001	43.1312
2002	45.71585
2003	45.7732
2004	46.70334
2005	51.48625
2006	48.54791
2007	49.99414
2008	56.92529
2009	57.438
2010	56.77157
2011	60.13945
2012	59.44857
2013	59.84265
2014	60.35476
2015	58.65096
2016	58.86642