Year	Percent
1980	29.91479
1981	32.09495
1982	35.17976
1983	38.51492
1984	37.45127
1985	43.54279
1986	41.6597
1987	36.85101
1988	38.42812
1989	32.42929
1990	30.38705
1991	31.00575
1992	45.58356
1993	43.46071
1994	51.29343
1995	45.37738
1996	42.28337
1997	32.73964
1998	34.77298
1999	38.81802
2000	48.65914
2001	60.60953
2002	60.24588
2003	58.93842
2004	63.0375
2005	52.0488
2006	46.5329
2007	29.33665
2008	42.9174
2009	45.73692
2010	61.70208
2011	67.65109
2012	67.9105
2013	45.96062
2014	51.70694
2015	53.97221
2016	55.62356
2017	47.15994