Year	Percent
1973	18.75253
1974	19.7256
1975	20.76421
1977	25.26509
1978	27.81871
1979	30.31507
1980	31.81634
1981	33.58032
1982	35.84686
1983	36.92066
1984	37.96753
1985	45.29141
1986	44.55758
1987	44.5542
1988	40.43886
1989	34.9081
1990	41.26837
1991	38.30165
1992	37.5197
1993	38.20488
1994	38.64201
1995	40.09357
1996	41.32205
1997	43.26036
1998	46.23506
1999	48.9066
2000	51.7582
2001	54.26645
2002	56.76753
2003	62.70658
2004	70.88901
2005	75.57794
2006	78.97895
2007	79.35275
2008	78.43755
2009	78.50361
2010	82.78959
2011	87.01091
2012	96.35015
2013	95.34892
2014	95.20776
2015	94.96626
2016	94.2387