Year	Percent
1975	0.53409
1976	0.89861
1978	0.72
1979	0.88956
1980	0.66839
1981	0.40387
1982	0.99008
1983	2.03537
1984	2.08391
1985	2.11956
1986	4.26449
1987	6.45215
1988	8.29947
1989	12.14475
1990	15.6256
1991	32.67886
1992	38.15745
1993	40.11399
1994	24.6765
1995	25.1876
1996	25.97976
1997	31.29312
1998	17.42553
1999	25.66402
2000	17.68649
2001	16.68526
2002	13.46202
2003	16.80061
2004	21.91167
2005	27.25179
2006	35.71353
2007	37.78152
2008	21.08624
2009	39.11419
2010	42.95185
2011	34.62037
2012	43.71501
2013	41.27416
2014	36.53764
2015	34.39171
2016	32.68986
2017	36.26521