Year	Percent
1960	3.02093
1961	3.00349
1962	2.97719
1963	2.94861
1964	2.92117
1965	2.89145
1966	2.86229
1967	2.82268
1968	2.7592
1969	2.66784
1970	2.56118
1971	2.45451
1972	2.36268
1973	2.29027
1974	2.24277
1975	2.21527
1976	2.18947
1977	2.16761
1978	2.16844
1979	2.19506
1980	2.23706
1981	2.28233
1982	2.31724
1983	2.33597
1984	2.33318
1985	2.3137
1986	2.28364
1987	2.25073
1988	2.21753
1989	2.18632
1990	2.15202
1991	2.11974
1992	2.07327
1993	1.99042
1994	1.86325
1995	1.70855
1996	1.54879
1997	1.40501
1998	1.28228
1999	1.18913
2000	1.12001
2001	1.05853
2002	1.00135
2003	0.96072
2004	0.93823
2005	0.93087
2006	0.9277
2007	0.92989
2008	0.94812
2009	0.98422
2010	1.03059
2011	1.08386
2012	1.12875
2013	1.14961
2014	1.138
2015	1.10325
2016	1.06039
2017	1.02229