Year	Percent
1960	3.05956
1961	2.90177
1962	2.96938
1963	3.10421
1964	3.07481
1965	3.09761
1966	3.36947
1967	3.12035
1968	2.98643
1969	2.731
1970	2.32042
1971	2.52421
1972	2.6958
1973	2.47556
1974	2.33442
1975	2.22687
1976	2.06104
1977	2.13169
1978	2.11923
1979	2.11269
1980	1.98832
1981	2.05311
1982	2.26085
1983	2.2734
1984	2.2645
1985	2.18305
1986	2.22902
1987	2.32283
1988	2.33693
1989	2.28459
1990	2.1204
1991	2.09566
1992	1.97517
1993	2.01439
1994	1.93207
1995	1.65484
1996	1.79086
1997	1.83393
1998	1.85401
1999	1.89774
2000	1.96286
2001	1.89331
2002	1.92355
2003	1.92671
2004	1.89704
2005	1.80966
2006	1.71982
2007	1.63244
2008	1.72509
2009	1.7529
2010	1.69559
2011	1.67509
2012	1.62738
2013	1.5908
2014	1.4673
2015	1.38051
2016	1.51768
2017	1.52231