Year	Percent
1968	47.73369
1969	48.19018
1970	50.80172
1971	53.98455
1972	61.58378
1973	99.70399
1974	62.93606
1975	73.33374
1976	59.72957
1977	57.42063
1978	49.31671
1979	54.85639
1980	63.4558
1981	62.81869
1982	50.73172
1983	38.46866
1984	34.52194
1985	30.07111
1986	26.703
1987	30.86177
1988	31.32377
1989	33.74568
1990	40.33479
1991	38.30839
1992	39.1068
1993	34.35283
1994	34.00095
1995	37.33786
1996	40.02284
1997	39.15863
1998	29.63238
1999	34.66649
2000	43.40527
2001	39.63372
2002	40.94879
2003	45.85417
2004	50.98533
2005	57.05074
2006	59.83191
2007	59.93744
2008	62.1115
2009	47.08862
2010	49.56979
2011	56.04924
2012	54.27084
2013	51.91797
2014	46.87529
2015	33.32117
2016	31.1442
2017	33.53853