Year	Percent
1960	1.56938
1961	1.55994
1962	1.55682
1963	1.58174
1964	1.64407
1965	1.7205
1966	1.81597
1967	1.87195
1968	1.81529
1969	1.61753
1970	1.33038
1971	1.03895
1972	0.80008
1973	0.60932
1974	0.4887
1975	0.43557
1976	0.39073
1977	0.38458
1978	0.51363
1979	0.80972
1980	1.22254
1981	1.71142
1982	2.17286
1983	2.52386
1984	2.72014
1985	2.82476
1986	2.81233
1987	2.85915
1988	3.17132
1989	3.81079
1990	4.58
1991	5.36937
1992	5.85722
1993	5.81109
1994	5.18293
1995	4.2416
1996	3.26677
1997	2.49472
1998	1.9632
1999	1.7541
2000	1.77274
2001	1.82903
2002	1.83572
2003	1.87029
2004	1.919
2005	1.97728
2006	2.06215
2007	2.15543
2008	2.21769
2009	2.23559
2010	2.22621
2011	2.20813
2012	2.2074
2013	2.23644
2014	2.30404
2015	2.39392
2016	2.48623
2017	2.55858