Year	Percent
1960	2.00479
1961	2.21591
1962	1.72961
1963	1.50801
1964	1.74419
1965	1.28772
1966	1.31747
1967	1.42105
1968	1.44268
1969	1.31424
1970	1.56167
1971	1.47526
1972	1.41452
1973	1.39842
1974	1.31154
1975	1.73998
1976	1.86239
1977	2.3815
1978	2.48802
1979	2.23819
1980	2.22003
1981	2.71504
1982	4.04005
1983	4.59237
1984	3.02227
1985	2.56757
1986	2.29317
1987	2.0049
1988	2.307
1989	2.317
1990	2.01281
1991	2.00186
1992	1.86927
1993	1.89049
1994	1.90024
1995	1.90185
1996	2.02925
1997	1.89538
1998	1.84657
1999	1.71655
2000	1.75327
2001	1.72408
2002	1.67747
2003	1.65791
2004	1.58529
2005	1.4516
2006	1.44637
2007	1.26101
2008	1.29057
2009	1.29496
2010	1.29665
2011	1.56127
2012	1.51234
2013	1.64178
2014	1.90878
2015	2.26965
2016	2.34588
2017	2.07008