Year	Percent
1971	5.82457
1973	10.82768
1974	10.97067
1975	11.67647
1976	10.94462
1977	11.21404
1978	11.28722
1979	11.47471
1980	11.73275
1981	12.08743
1982	14.48926
1983	19.80545
1984	27.24201
1985	28.54611
1986	29.66597
1987	29.18306
1988	40.12095
1989	33.97499
1990	41.88653
1991	46.41981
1992	49.64769
1993	53.11211
2000	24.92617
2001	25.35312
2002	25.85553
2003	30.42914
2004	32.72387
2005	34.94944
2007	39.5006
2008	42.34246
2009	49.00309
2010	52.08395
2011	56.97446
2012	63.94147
2013	72.20919
2014	71.32177
2015	66.4269
2016	69.79504