Year	Percent
1980	55.9793
1981	67.50889
1982	60.66054
1983	52.40848
1984	51.29915
1985	39.92756
1986	45.99563
1987	51.1472
1988	44.54893
1989	46.28697
1990	49.94038
1991	49.60516
1992	48.69182
1993	49.99565
1994	45.76072
1995	49.31859
1996	51.70819
1997	50.83507
1998	51.37834
1999	50.31477
2000	44.55041
2001	47.66953
2002	48.07313
2003	52.47147
2004	42.07922
2005	40.31256
2006	41.55988
2007	55.81752
2008	66.85305
2009	73.1308
2010	60.65621
2011	57.475
2012	60.15507
2013	58.0499
2014	63.42866
2015	68.69096
2016	63.96618
2017	47.49698