Year	Percent
1960	7.07509
1961	7.85613
1962	8.49942
1963	8.79305
1964	8.82562
1965	8.71904
1966	8.67827
1967	8.69107
1968	8.59781
1969	8.36427
1970	8.13489
1971	7.67203
1972	7.37229
1973	7.79888
1974	9.00411
1975	10.42236
1976	11.84022
1977	12.4751
1978	11.86058
1979	10.09952
1980	7.91833
1981	5.63907
1982	3.96267
1983	2.94725
1984	3.3377
1985	4.99423
1986	6.81469
1987	7.8938
1988	7.865
1989	6.6537
1990	4.86738
1991	2.95383
1992	1.40555
1993	0.61824
1994	0.68569
1995	1.34101
1996	2.14854
1997	2.70804
1998	2.99113
1999	2.88315
2000	2.52813
2001	2.14622
2002	1.88711
2003	1.70732
2004	1.64721
2005	1.66776
2006	1.70011
2007	1.70352
2008	1.71782
2009	1.73417
2010	1.76657
2011	1.80726
2012	1.8414
2013	1.85289
2014	1.83024
2015	1.79122
2016	1.73916
2017	1.69759