Year	Percent
1978	31.19227
1979	22.10786
1980	25.35399
1981	36.04259
1982	31.10215
1983	29.11546
1984	24.9815
1985	15.72361
1986	52.07694
1987	18.9909
1988	15.10513
1989	13.31595
1990	14.73309
1991	46.87507
1997	19.37203
1998	21.03425
1999	16.48477
2000	21.24269
2001	17.36942
2002	19.78162
2003	43.54161
2004	22.2314
2005	9.99759
2006	3.17129
2007	2.37065
2008	2.95307
2009	3.48212
2010	1.85816
2011	2.33908
2012	2.19556
2013	2.80817
2014	3.57365
2015	6.02734
2016	8.56406