Year	Percent
1960	2.7834
1961	2.49381
1962	2.79028
1963	2.26139
1964	2.30233
1965	2.29253
1966	2.61009
1967	1.46247
1968	1.96155
1969	2.28884
1970	2.16442
1971	3.57178
1972	2.02808
1973	1.71602
1974	2.71808
1975	1.41534
1976	1.18529
1977	1.30662
1978	1.34134
1979	1.25761
1980	1.39326
1981	1.7597
1982	1.63253
1983	1.21669
1984	1.09719
1985	1.33347
1986	1.60393
1987	1.48591
1988	1.60229
1989	1.65747
1990	1.44487
1991	1.23946
1992	1.07513
1993	0.82814
1994	0.90691
1995	1.05502
1996	1.15939
1997	0.96407
1998	0.88497
1999	0.98499
2000	1.03214
2001	1.18796
2002	1.36552
2003	1.37756
2004	1.30153
2005	1.46058
2006	1.61464
2007	0.76862
2008	2.14657
2009	2.20222
2010	1.69529
2011	1.52796
2012	1.90495
2013	1.87536
2014	1.65277
2015	1.57964
2016	1.61366
2017	1.71153