Year	Percent
1975	15.21642
1976	14.31652
1977	11.69685
1978	12.20589
1979	15.79299
1980	22.36869
1981	24.76465
1982	22.21242
1983	19.70911
1984	21.70751
1985	24.14983
1986	27.86845
1987	29.89571
1988	26.57069
1989	9.52356
1990	8.45786
1991	10.45393
1992	25.1333
1993	8.34944
1994	6.49199
1995	5.24747
1996	4.79107
1997	5.98769
1998	5.06076
1999	6.72863
2000	8.963
2001	10.15021
2002	9.8541
2003	9.88448
2004	11.11546
2005	9.51972
2006	6.83259
2007	5.32894
2008	4.49964
2009	5.76897
2010	4.51638
2011	6.91021
2012	16.03477
2013	11.43748
2014	22.05949
2015	18.78041
2016	10.98283