Year	Percent
1960	6.05252
1961	6.20402
1962	6.27568
1963	6.22381
1964	6.02754
1965	5.75696
1966	5.50326
1967	5.24853
1968	4.92124
1969	4.51182
1970	4.07232
1971	3.61825
1972	3.23374
1973	2.98105
1974	2.90175
1975	2.93568
1976	3.00102
1977	3.0311
1978	3.06558
1979	3.05545
1980	3.07075
1981	3.23169
1982	3.22066
1983	3.15851
1984	3.04921
1985	2.91119
1986	2.74993
1987	2.6163
1988	2.53111
1989	2.50769
1990	2.46247
1991	2.13388
1992	2.18528
1993	2.15274
1994	2.00462
1995	1.80355
1996	1.5613
1997	1.37987
1998	1.3349
1999	1.46396
2000	1.68383
2001	1.79636
2002	2.01952
2003	2.16017
2004	2.17563
2005	2.11416
2006	2.03021
2007	1.96746
2008	1.88701
2009	1.80795
2010	1.72105
2011	1.63671
2012	1.54914
2013	1.46583
2014	1.38517
2015	1.30877
2016	1.23325
2017	1.16212