Year	Percent
1971	3.01891
1973	6.63134
1974	7.34232
1975	7.99438
1976	7.79481
1977	7.85495
1978	8.17125
1979	8.54588
1980	8.74726
1981	8.91135
1982	10.80879
1983	14.74051
1984	20.17155
1985	20.63189
1986	22.03566
1987	21.40617
1988	30.38611
1989	27.24558
1990	34.19567
1991	42.82506
1992	42.83692
1993	46.12559
2000	22.54683
2001	22.49647
2002	22.66845
2003	25.64517
2004	26.19015
2005	30.09082
2007	35.65896
2008	38.70919
2009	46.6069
2010	50.17287
2011	56.2331
2012	64.6667
2013	74.72942
2014	75.22813
2015	70.66457
2016	74.52029