Year	Percent
1971	9.57332
1972	8.91754
1973	9.09233
1974	8.52514
1975	9.64448
1976	9.59836
1977	10.69871
1978	11.06454
1979	12.18412
1980	11.8544
1981	13.22412
1982	13.48841
1983	14.32795
1984	15.06088
1985	17.60695
1987	19.94905
1988	21.28867
1989	20.88016
1990	24.60764
1991	24.63355
1992	31.51266
1993	32.82103
1994	33.5381
1995	21.80421
1996	26.96514
1999	27.59959
2000	29.83723
2001	31.58821
2002	31.99355
2003	33.29828
2004	34.56199
2005	35.87611
2006	36.61657
2007	39.12809
2008	43.28088
2009	47.26896
2010	49.89637
2012	58.65169
2013	62.18212
2014	59.05706
2015	60.56146
2016	59.47017