Year	Percent
1960	2.69073
1961	2.48563
1962	2.30994
1963	2.19829
1964	2.47283
1965	2.35556
1966	2.63927
1967	2.62372
1968	2.72768
1969	2.56623
1970	2.63203
1971	2.3167
1972	2.18327
1973	1.97304
1974	2.06538
1975	2.08476
1976	1.93603
1977	2.1159
1978	2.20987
1979	2.15964
1980	3.02279
1981	2.72938
1982	2.58286
1983	2.43836
1984	2.37762
1985	2.36463
1986	2.36759
1987	2.40728
1988	2.07871
1989	2.14993
1990	2.32778
1991	2.25634
1992	2.06937
1993	1.89912
1994	1.82871
1995	1.81535
1996	1.78188
1997	1.70397
1998	1.69528
1999	1.61934
2000	1.57671
2001	1.47228
2002	1.38481
2003	1.35006
2004	1.25448
2005	1.21143
2006	1.31165
2007	1.24819
2008	1.24646
2009	1.33757
2010	1.31716
2011	1.23475
2012	1.189
2013	1.12013
2014	1.13809
2015	1.1117
2016	1.13663
2017	1.15844