Year	Percent
1960	28.65694
1961	56.68522
1962	29.32416
1963	29.61297
1964	34.65333
1965	34.05927
1966	33.80889
1967	15.40935
1968	22.50753
1969	14.97697
1970	11.69888
1971	16.95088
1972	13.08526
1973	8.94535
1974	7.30736
1975	11.84138
1976	8.98764
1977	16.86117
1978	12.73823
1979	13.78861
1980	17.60085
1981	18.50515
1982	14.38116
1983	10.43388
1984	7.36648
1985	18.82706
1986	7.99798
1987	7.7887
1988	7.69111
1989	6.26598
1990	13.23973
1991	17.37501
1992	10.20825
1993	9.30729
1994	7.47942
1995	5.05038
1996	6.15011
1997	4.83339
1998	4.56985
1999	6.34094
2000	4.36848
2001	4.53212
2002	3.17045
2003	3.86578
2004	4.23209
2005	3.88108
2006	5.19304
2007	4.5522
2008	4.01923
2009	3.2127
2010	3.10265
2011	3.97117
2012	4.27511
2013	5.42264
2014	6.11034
2015	4.55669
2016	5.78383
2017	6.46896
2018	1.99947
2019	1.90594
2020	5.23577
2021	2.22919