Year	Percent
1960	5.14421
1961	5.18977
1962	5.24217
1963	5.28019
1964	5.33667
1965	5.36895
1966	5.39744
1967	5.38693
1968	5.44859
1969	5.54849
1970	5.68401
1971	5.78297
1972	5.8134
1973	5.74056
1974	5.56338
1975	5.30011
1976	5.09123
1977	4.85334
1978	4.38688
1979	3.60384
1980	3.07924
1981	2.00513
1982	1.11248
1983	0.57205
1984	0.62247
1985	1.16711
1986	1.80766
1987	2.48778
1988	3.64261
1989	2.45807
1990	4.34651
1991	6.32015
1992	7.74309
1993	8.08133
1994	7.31438
1995	5.98967
1996	4.5585
1997	3.50493
1998	3.00239
1999	3.23547
2000	3.91223
2001	4.66284
2002	5.13467
2003	5.23046
2004	5.12439
2005	4.76865
2006	4.12319
2007	3.65049
2008	3.40419
2009	3.4571
2010	3.697
2011	3.98009
2012	4.15406
2013	4.19298
2014	4.05739
2015	3.81792
2016	3.56025
2017	3.40585