Year	Percent
1974	13.77658
1975	14.0638
1976	15.07627
1977	18.19377
1978	20.43387
1979	21.86437
1980	22.63708
1981	24.70204
1982	21.74339
1983	25.61191
1984	24.94808
1985	26.4573
1986	26.64834
1987	26.80024
1988	21.63688
1989	22.66297
1990	25.15203
1991	28.52246
1992	32.77082
1993	33.94135
1994	36.43804
1995	46.74086
1996	54.86607
1999	58.06767
2000	57.42381
2001	60.49464
2002	62.40664
2004	55.89968
2005	56.09394
2006	56.33297
2007	57.56056
2008	61.76858
2009	64.24763
2010	66.50936
2011	68.85794
2012	71.39335
2013	76.88503
2014	77.58194