Year	Percent
1960	2.37624
1961	2.04677
1962	2.04545
1963	1.76521
1964	1.90995
1965	2.06957
1966	1.82422
1967	1.80442
1968	1.92397
1969	2.37062
1970	1.83369
1971	1.85403
1972	1.99002
1973	1.97657
1974	2.01589
1975	2.36681
1976	2.20069
1977	3.08037
1978	2.14273
1979	1.98749
1980	1.78122
1981	1.67784
1982	1.654
1983	1.57478
1984	1.48523
1985	1.77974
1986	1.83739
1987	1.96632
1988	1.97763
1989	1.92399
1990	1.89032
1991	1.77836
1992	1.66721
1993	1.82142
1994	1.55934
1995	2.34132
1996	1.9504
1997	2.10417
1998	2.35723
1999	1.75193
2000	1.45208
2001	1.56938
2002	1.76889
2003	2.27855
2004	1.94033
2005	2.2984
2006	2.02983
2007	2.56824
2008	2.66504
2009	3.11742
2010	3.01055
2011	3.09511
2012	2.94545
2013	2.88662
2014	2.76119
2015	2.57506
2016	2.55198
2017	2.44525