Year	Percent
1960	1.88432
1961	2.14326
1962	3.09942
1963	3.51514
1964	3.1808
1965	3.19095
1966	3.16524
1967	3.11736
1968	2.38537
1969	2.05492
1970	2.25955
1971	3.37417
1972	1.9672
1973	1.69025
1974	1.57578
1975	1.74027
1976	1.4936
1977	1.43849
1978	1.55032
1979	1.67393
1980	1.83012
1981	1.75512
1982	1.71385
1983	2.21994
1984	2.32589
1985	2.05402
1986	1.94462
1987	1.98314
1988	2.19924
1989	2.18818
1990	1.86016
1991	1.85348
1992	2.10668
1993	2.52527
1994	2.50841
1995	2.83163
1996	4.44539
1997	2.80179
1998	3.44099
1999	3.76274
2000	3.03168
2001	3.32387
2002	3.41713
2003	3.46399
2004	3.46502
2005	3.35287
2006	3.27613
2007	3.26674
2008	3.70974
2009	3.86329
2010	3.63115
2011	3.07278
2012	3.16678
2013	3.28882
2014	3.1304
2015	3.12488
2016	3.06917
2017	3.10223