Year	Percent
1960	9.04145
1961	9.31715
1962	8.95863
1963	8.83529
1964	7.64637
1965	7.43439
1966	7.70367
1967	8.49482
1968	7.13702
1969	6.66667
1970	5.7469
1971	6.23507
1972	6.15515
1973	5.92211
1974	7.17207
1975	6.32524
1976	5.5613
1977	5.81997
1978	5.58205
1979	5.00188
1980	5.30465
1981	5.43192
1982	4.70217
1983	3.65363
1984	3.95745
1985	4.28584
1986	4.12008
1987	4.6263
1988	4.76801
1989	4.39916
1990	3.77706
1991	3.7435
1992	3.14921
1993	3.42257
1994	3.75545
1995	3.12159
1996	3.41659
1997	3.2659
1998	3.03418
1999	2.8464
2000	2.61475
2001	2.81245
2002	2.95697
2003	2.65398
2004	2.41172
2005	2.08512
2006	2.05098
2007	2.35591
2008	2.57249
2009	2.3995
2010	2.10779
2011	2.04389
2012	1.97671
2013	1.92685
2014	2.12575
2015	2.23398
2016	2.41419
2017	2.4938
2018	2.2607
2019	1.95032
2020	2.58242
2021	2.5573
2022	2.83028