Year	Percent
1972	7.92602
1973	9.78041
1974	5.94386
1975	5.12004
1976	4.87761
1977	8.47006
1978	9.83627
1979	12.05828
1980	12.28065
1981	14.48861
1982	14.06548
1983	19.3878
1984	20.60981
1985	25.0911
1986	31.39461
1987	33.35052
1988	41.60029
1989	24.8502
1990	24.37063
1991	28.7907
1992	25.86656
1993	20.91738
1994	18.69009
1995	16.68908
1996	25.89736
1997	22.60244
1998	22.16124
1999	13.73575
2000	20.06506
2001	19.51528
2002	14.14503
2003	23.63933
2004	14.47447
2005	11.93463
2006	11.34517
2007	10.57597
2008	20.90448
2009	5.9992
2010	5.85323
2011	6.52864
2012	6.36493
2013	6.24377
2014	8.17625
2015	14.32028
2016	17.22771