Year	Percent
1977	10.74836
1978	20.11494
1979	17.78721
1980	27.7825
1981	36.04091
1982	35.02915
1983	29.26548
1984	31.06566
1985	39.8427
1986	53.69301
1987	37.43156
1988	30.88581
1989	30.91861
1990	29.31879
1991	24.8706
1992	24.85878
1993	22.37802
1994	22.48538
1995	24.93952
1996	15.90851
1997	14.39074
1998	14.86315
1999	14.09087
2000	13.50432
2001	9.52679
2002	7.72147
2003	6.7421
2004	10.54221
2005	12.50129
2006	8.87843
2007	3.8319
2008	3.12134
2009	2.86024
2010	1.70638
2011	1.41622
2012	2.0539
2013	3.14885
2014	3.95859
2015	4.28957
2016	5.0283