Year	Percent
1970	47.45552
1971	44.85065
1972	45.78122
1973	42.88253
1974	41.37979
1975	47.772
1976	48.0897
1977	46.1544
1978	51.61293
1979	51.58866
1980	42.19533
1981	49.27083
1982	46.75968
1983	42.44116
1984	41.31734
1985	46.48738
1986	45.24922
1987	53.50911
1988	53.98622
1989	48.65899
1990	56.93605
1991	51.2763
1992	47.83462
1993	52.84461
1994	52.2602
1995	51.79759
1996	54.24518
1997	53.64573
1998	61.41626
1999	55.04083
2000	41.72867
2001	37.50795
2002	41.83199
2003	42.34588
2004	41.99168
2005	44.35829
2006	42.2604
2007	43.17569
2008	46.66772
2009	43.99992
2010	45.08805
2011	45.02246
2012	46.8925
2013	44.13561
2014	41.13235
2015	46.78813
2016	46.34836
2017	49.15781
2018	30.7237
2019	30.39658
2020	30.86324