Year	Percent
1960	12.57012
1961	11.81306
1962	11.65405
1963	12.87991
1964	12.97062
1965	11.96904
1966	15.38015
1967	14.72217
1968	14.37864
1969	13.57065
1970	12.56666
1971	11.94779
1972	11.79736
1973	12.09519
1974	12.26696
1975	12.34369
1976	11.94957
1977	11.03707
1978	11.07164
1982	13.53656
1983	14.16087
1984	14.86464
1985	15.48835
1986	15.50821
1987	15.71196
1988	13.00565
1989	13.76062
1990	14.67545
1991	12.12606
1992	11.69328
1993	12.17611
1994	10.012
1995	10.16232
1996	14.57444
1997	14.03132
1998	14.56473
1999	15.53258
2000	20.07972
2001	18.00896
2002	19.71449
2003	21.4017
2004	24.04821
2005	26.87539
2006	26.18937
2007	28.89557
2008	31.74036
2009	23.07046
2010	26.91925
2011	26.19136
2012	3.32567
2013	2.69372
2014	2.52553
2015	2.07317
2016	2.32
2017	2.31051