Year	Percent
1970	26.38856
1971	26.434
1972	23.7295
1973	21.96674
1974	21.43388
1975	20.28598
1976	22.1918
1977	26.3838
1978	29.4808
1979	30.31015
1980	32.42064
1981	34.01305
1982	33.69977
1983	36.0684
1984	31.93289
1985	75.62106
1986	64.0115
1987	72.58399
1988	80.60075
1989	65.2643
1990	66.35177
1991	49.11542
1992	43.48369
1993	40.37105
1994	31.57313
1995	29.07696
1996	25.36197
1997	22.92731
1998	22.05821
1999	23.12384
2000	20.11768
2001	21.89989
2002	25.8654
2003	36.59744
2004	38.66027
2005	24.14905
2006	27.03724
2007	25.59852
2008	22.79621
2009	25.40756
2010	25.96012
2011	27.20623
2012	37.96601
2013	40.61086
2014	42.3745
2015	40.96325
2016	41.13265