Year	Percent
1960	1.91789
1961	2.0608
1962	2.17883
1963	2.22923
1964	2.19141
1965	2.09406
1966	1.97358
1967	1.87029
1968	1.79632
1969	1.76561
1970	1.75867
1971	1.76106
1972	1.73613
1973	1.65653
1974	1.5069
1975	1.31249
1976	1.11502
1977	0.9428
1978	0.79305
1979	0.67627
1980	0.59031
1981	0.49734
1982	0.41808
1983	0.41333
1984	0.50367
1985	0.65602
1986	0.84043
1987	0.99308
1988	1.06525
1989	1.02522
1990	0.90725
1991	0.76726
1992	0.65223
1993	0.5646
1994	0.52161
1995	0.5098
1996	0.50276
1997	0.4821
1998	0.45397
1999	0.41406
2000	0.36595
2001	0.32059
2002	0.2808
2003	0.23939
2004	0.19595
2005	0.15354
2006	0.10611
2007	0.06596
2008	0.05366
2009	0.0782
2010	0.12758
2011	0.19041
2012	0.24185
2013	0.26341
2014	0.24156
2015	0.1892
2016	0.12687
2017	0.07538