Year	Percent
1960	4.05388
1961	4.0754
1962	5.1885
1963	5.15536
1964	5.10436
1965	5.02968
1966	4.96071
1967	4.89255
1968	4.82099
1969	4.73411
1970	4.65433
1971	4.56746
1972	4.43161
1973	3.70179
1974	3.68729
1975	3.67891
1976	3.67922
1977	3.66198
1978	3.62742
1979	3.56825
1980	3.48947
1981	3.40332
1982	3.05993
1983	2.99676
1984	2.95713
1985	2.92766
1986	2.89854
1987	2.85973
1988	2.81656
1989	2.76276
1990	2.70489
1991	2.64719
1992	2.58786
1993	2.50848
1994	2.4739
1995	2.368
1996	2.25837
1997	2.1564
1998	2.06909
1999	1.99757
2000	1.93806
2001	1.88245
2002	1.83259
2003	1.79502
2004	1.7682
2005	1.74998
2006	1.73667
2007	1.72416
2008	1.55482
2009	1.49564
2010	1.5226
2011	1.55107
2012	1.57551
2013	1.58026
2014	1.56354
2015	1.53188
2016	1.49286
2017	1.45823