Year	Percent
1960	0.68202
1961	0.83437
1962	2.3457
1963	2.38306
1964	2.60516
1965	1.52482
1966	1.64948
1967	1.32507
1968	1.17848
1969	1.24672
1970	1.17224
1971	1.17717
1972	1.13985
1973	1.23519
1974	1.15191
1975	2.81118
1976	3.12383
1977	3.04327
1978	3.28315
1979	2.69861
1980	2.74669
1981	2.84269
1982	3.0033
1983	2.93218
1984	3.01717
1985	1.83653
1986	2.62189
1987	2.25259
1988	2.31081
1989	2.74077
1990	2.70489
1991	2.16687
1992	2.04965
1993	1.86253
1994	1.42288
1995	1.38304
1996	1.28709
1997	1.41706
1998	1.27636
1999	1.38553
2000	1.39243
2001	1.29961
2002	1.32482
2003	1.20687
2004	1.35752
2005	1.35177
2006	1.24878
2007	1.59227
2008	1.3979
2009	1.52145
2010	1.37752
2011	1.29476
2012	1.32302
2013	1.37104
2014	1.41477
2015	1.33035
2016	1.23654
2017	1.43623