Year	Percent
1960	4.83222
1961	4.88366
1962	4.94187
1963	4.98685
1964	5.05206
1965	5.07114
1966	5.11317
1967	5.13801
1968	5.32323
1969	5.24361
1970	5.14494
1971	5.03774
1972	4.96072
1973	4.91882
1974	4.95904
1975	5.03558
1976	4.07923
1977	3.28687
1978	3.40455
1979	3.54511
1980	3.69628
1981	3.85909
1982	3.98398
1983	3.98203
1984	3.82642
1985	3.57647
1986	3.29544
1987	3.07518
1988	2.97963
1989	2.66885
1990	2.52957
1991	2.73374
1992	2.87659
1993	2.94042
1994	2.89951
1995	2.79137
1996	2.66433
1997	2.56356
1998	2.46744
1999	2.39419
2000	2.33021
2001	2.25051
2002	2.16578
2003	2.09408
2004	2.04217
2005	2.05209
2006	2.09835
2007	2.12839
2008	2.04896
2009	1.83217
2010	1.54194
2011	1.21113
2012	0.96256
2013	0.90123
2014	1.09268
2015	1.47048
2016	1.9047
2017	2.28046