Year	Percent
1975	24.43363
1976	19.5971
1977	20.2176
1978	19.98545
1979	22.66113
1980	26.52302
1981	25.90542
1982	22.21971
1983	19.47393
1984	20.805
1985	22.0079
1986	21.52094
1987	21.27489
1988	20.36
1989	21.72026
1990	22.79241
1991	27.16808
1992	36.48523
1993	32.44745
1994	36.51953
1995	40.92045
1996	35.93955
1997	44.60979
1998	45.12096
1999	33.51408
2000	35.90766
2001	32.93896
2002	34.97255
2003	38.05493
2004	41.56981
2005	42.49506
2006	46.86448
2007	46.38753
2008	68.05479
2009	47.42431
2010	63.5019
2011	63.71822
2012	58.88123
2013	45.30508
2014	41.39484
2015	46.0228
2016	38.66857
2017	37.3962