Year	Percent
1960	1.61211
1961	1.56807
1962	1.51602
1963	1.46252
1964	1.40722
1965	1.3511
1966	1.30539
1967	1.25179
1968	1.14876
1969	0.97899
1970	0.77456
1971	0.54583
1972	0.35548
1973	0.26291
1974	0.30754
1975	0.48009
1976	0.89816
1977	1.03702
1978	1.13299
1979	1.15836
1980	1.13169
1981	1.0965
1982	1.08288
1983	1.06424
1984	1.04915
1985	1.03692
1986	1.04972
1987	1.04195
1988	1.03283
1989	1.03922
1990	1.06059
1991	1.07817
1992	1.08651
1993	1.08446
1994	1.07372
1995	1.0505
1996	1.0409
1997	1.04772
1998	0.97573
1999	0.84039
2000	0.6699
2001	0.47462
2002	0.30789
2003	0.21519
2004	0.22261
2005	0.30419
2006	0.41362
2007	0.50206
2008	0.56456
2009	0.57964
2010	0.56349
2011	0.54114
2012	0.46302
2013	0.4397
2014	0.44557
2015	0.45576
2016	0.46636
2017	0.47021