Year	Percent
1960	4.79027
1961	4.96906
1962	5.06054
1963	5.03294
1964	4.87778
1965	4.64445
1966	4.40823
1967	4.17688
1968	3.86764
1969	3.48219
1970	3.06137
1971	2.62764
1972	2.2611
1973	2.03109
1974	1.97013
1975	2.02317
1976	2.10598
1977	2.15847
1978	2.20869
1979	2.21776
1980	2.22187
1981	2.2228
1982	2.23986
1983	2.20544
1984	2.12134
1985	2.01082
1986	1.87588
1987	1.76659
1988	1.70523
1989	1.71
1990	1.76594
1991	1.84757
1992	1.90352
1993	1.87276
1994	1.72929
1995	1.53048
1996	1.29094
1997	1.11432
1998	1.07101
1999	1.20351
2000	1.46014
2001	1.7454
2002	1.9671
2003	2.10889
2004	2.12457
2005	2.06306
2006	1.97908
2007	1.91643
2008	1.83738
2009	1.75689
2010	1.67004
2011	1.57716
2012	1.48146
2013	1.38829
2014	1.29813
2015	1.21431
2016	1.12947
2017	1.04985