Year	Percent
1981	69.95587
1982	70.22934
1983	58.0063
1984	57.80033
1985	62.79199
1986	63.85266
1987	50.83144
1988	46.80279
1989	47.8011
1990	29.06733
1991	30.96436
1992	25.65487
1993	21.06596
1994	19.0666
1995	26.785
1996	26.20103
1997	25.03469
1998	30.46552
1999	31.68812
2000	29.01074
2001	25.17395
2002	24.64171
2003	32.26279
2004	31.18316
2005	37.52856
2006	35.88519
2007	38.70514
2008	43.56614
2009	34.37095
2010	42.08695
2011	58.15072
2012	55.89862
2013	53.27571
2014	35.1753
2015	26.41265
2016	29.3777
2017	36.15995