Year	Percent
1960	3.05804
1961	1.42222
1962	2.3129
1963	2.55359
1964	2.44669
1965	2.63644
1966	2.65688
1967	2.85852
1968	2.67738
1969	2.49892
1970	2.29402
1971	2.69941
1972	2.82927
1973	2.47099
1974	2.30776
1975	2.59102
1976	1.88749
1977	2.06795
1978	2.10576
1979	1.91586
1980	1.69552
1981	1.52169
1982	2.24877
1983	2.97074
1984	2.29205
1985	1.36962
1986	1.64997
1987	1.6337
1988	1.81611
1989	2.7936
1990	1.51804
1991	1.84034
1992	1.64348
1993	2.14525
1994	1.59075
1995	1.54906
1996	1.03948
1997	1.79529
1998	1.58856
1999	1.4372
2000	1.52657
2001	1.55511
2002	1.15337
2003	1.18269
2004	1.2883
2005	1.83171
2006	1.97849
2007	1.88899
2008	1.79355
2009	1.23107
2010	1.01349
2011	1.13041
2012	1.34147
2013	1.66955
2014	1.16182
2015	0.94138
2016	0.45405
2017	0.48784