Year	Percent
1960	0.71726
1961	2.93081
1962	3.99705
1963	3.83994
1964	3.73441
1965	3.63888
1966	3.55839
1967	3.48947
1968	3.3913
1969	3.25663
1970	3.07042
1971	1.96855
1972	1.50941
1973	1.43267
1974	1.34226
1975	1.26426
1976	1.17048
1977	1.11202
1978	1.06211
1979	1.00919
1980	0.98113
1981	0.68652
1982	0.55218
1983	0.51561
1984	0.46638
1985	0.48195
1986	0.53884
1987	0.64985
1988	0.71801
1989	0.59254
1990	0.5222
1991	0.90504
1992	1.12915
1993	1.13873
1994	1.10447
1995	0.97282
1996	0.87888
1997	1.09966
1998	1.3325
1999	1.40458
2000	1.24407
2001	0.97588
2002	1.00301
2003	1.04291
2004	0.99873
2005	1.03704
2006	1.15882
2007	1.39841
2008	1.61887
2009	1.62848
2010	1.60916
2011	1.74246
2012	1.8394
2013	1.72363
2014	1.63215
2015	1.5198
2016	1.33422
2017	1.3798