Year	Percent
1987	41.5493
1988	42.17687
1989	42.36111
1990	40
1991	27.60417
1992	35.65684
1993	46.88874
1994	57.7721
1995	25.5019
1996	13.32629
1997	15.61013
1998	16.45873
1999	19.05561
2000	22.99463
2001	24.46137
2002	29.22917
2003	31.83762
2004	31.55575
2005	33.74824
2006	32.86555
2007	31.20572
2008	28.61997
2009	29.73949
2010	34.95113
2011	36.24242
2012	38.15052
2013	44.68923
2014	42.94362
2015	44.73796
2016	43.60424
2017	50.4107