Year	Percent
1960	17.41522
1961	17.1101
1962	17.64942
1963	18.37508
1964	18.77521
1965	18.06114
1966	17.94587
1967	20.21146
1968	20.6815
1969	20.0606
1970	19.38195
1971	18.81291
1972	19.18401
1973	20.04638
1974	23.95559
1975	22.97494
1976	22.70505
1977	25.37769
1978	24.11327
1979	29.29683
1980	30.36762
1981	30.12128
1982	24.63042
1983	27.27329
1984	26.16788
1985	25.9416
1986	23.56906
1987	28.33397
1988	34.4015
1989	37.48541
1990	41.65044
1991	42.50683
1992	40.98217
1993	40.92866
1994	43.00684
1995	48.22389
1996	45.25572
1997	46.81484
1998	42.30312
1999	44.26779
2000	56.45767
2001	57.01715
2002	54.32399
2003	55.17028
2004	61.44011
2005	69.45117
2006	65.41152
2007	61.00091
2008	69.02057
2009	54.83087
2010	60.76432
2011	68.82057
2012	68.72379
2013	65.28894
2014	62.51133
2015	57.1883
2016	53.54794