Year	Percent
1978	22.02532
1979	32.18894
1980	48.4
1981	44.81944
1982	47.9475
1983	49.12381
1984	31.13617
1985	33.33696
1986	35.58958
1987	38.17708
1988	37.68
1989	40.06538
1990	44.17451
1991	56.66607
1992	59.58677
1993	57.95797
1994	59.024
1995	59.31171
1996	60.97529
1997	61.94615
1998	60.86337
1999	61.40841
2000	58.28733
2001	59.47123
2002	57.7869
2003	57.61918
2004	56.91555
2005	59.14632
2006	63.07907
2007	63.10816
2008	63.12745
2009	63.00502
2010	63.74968
2011	65.70383
2012	66.63262
2013	67.50127