Year	Percent
1975	10.51604
1976	10.31306
1977	10.88236
1978	11.34543
1979	9.04316
1980	7.57537
1981	7.848
1982	8.91283
1983	10.79356
1984	10.84879
1985	24.43036
1986	24.72197
1987	16.89241
1988	17.9713
1989	26.20235
1990	20.13129
1991	19.90523
1992	15.48148
1993	21.35288
1994	22.62918
1995	22.27849
1996	26.5524
1997	37.19461
1998	48.78032
1999	65.09976
2000	65.14221
2001	54.94319
2002	32.99512
2003	43.06229
2004	42.37009
2005	42.01202
2006	54.54252
2007	61.19844
2008	29.59679
2009	37.81022
2010	41.8402
2011	31.52196
2012	41.9391
2013	51.59492
2014	44.68555
2015	50.82933
2016	49.34278
2017	61.51625