Year	Percent
1961	0.26556
1962	0.54688
1963	0.83996
1964	2.15711
1965	1.89539
1966	1.33748
1967	1.33974
1968	1.35886
1969	1.28224
1970	1.3684
1971	1.40831
1972	1.47564
1973	1.69492
1974	1.49195
1975	1.85659
1976	2.49523
1977	3.07227
1978	2.71429
1979	2.24906
1980	2.19463
1981	2.37248
1982	2.25918
1983	2.09698
1984	2.18515
1985	2.50798
1986	2.84506
1987	3.50349
1988	3.12491
1989	3.09407
1990	3.12249
1991	2.85935
1992	2.93123
1993	4.03066
1994	2.58431
1995	2.00364
2003	1.36569
2004	1.40607
2005	1.45743
2008	1.72219
2009	1.63802
2010	1.65881
2011	1.5711
2012	1.61489
2013	1.73271
2014	1.81565
2015	1.74824
2016	1.92517
2017	1.93526