Year	Percent
1960	9.79439
1961	9.75192
1962	9.78283
1963	9.78767
1964	9.861
1965	9.86792
1966	9.93969
1967	15.27211
1968	15.22237
1969	15.10561
1970	14.97843
1971	14.83945
1972	4.54402
1973	4.40317
1974	4.43575
1975	4.47445
1976	4.51662
1977	4.53233
1978	4.56531
1979	4.57401
1980	4.57475
1981	4.28819
1982	4.20137
1983	4.17816
1984	4.13103
1985	4.07016
1986	4.01355
1987	3.95919
1988	3.91793
1989	3.90163
1990	3.88492
1991	1.32305
1992	1.24174
1993	1.25211
1994	1.26059
1995	1.28205
1996	1.29834
1997	1.32199
1998	1.32581
1999	1.30612
2000	1.28982
2001	2.38345
2002	2.38823
2003	2.36328
2004	2.33308
2005	2.31867
2006	2.29623
2007	2.26973
2008	2.23674
2009	2.19586
2010	2.14987
2011	2.0951
2012	2.05863
2013	2.12626
2014	2.19999
2015	2.2777
2016	2.35557
2017	2.43215