Year	Percent
1980	22.70949
1981	21.51496
1982	23.87754
1983	20.80902
1984	19.37735
1985	18.44986
1986	15.46751
1987	15.56251
1988	19.21802
1989	20.71838
1990	23.19634
1991	27.59181
1992	88.51225
1993	62.29255
1994	38.95032
1995	34.51205
1996	32.02444
1997	34.19
1998	34.63704
1999	32.21302
2000	38.05334
2001	38.99879
2002	44.33537
2003	45.08471
2004	44.37489
2005	47.47123
2006	48.52105
2007	54.7882
2008	52.14931
2009	49.85417
2010	48.564
2011	51.97705
2012	47.57269
2013	46.95743
2014	47.19486
2015	44.53363
2016	45.74585
2017	46.55357