Year	Percent
1960	23.60046
1961	20.4918
1962	19.80472
1963	20.95408
1964	21.10971
1965	19.1358
1966	19.18819
1967	19.86302
1968	19.61415
1969	17.70683
1970	17.89474
1971	17.13641
1972	16.42512
1973	15.72848
1974	15.1171
1975	14.47689
1976	13.47754
1977	15.42553
1978	16.03631
1979	14.31373
1980	11.68147
1981	7.88259
1982	7.85915
1983	7.58258
1984	6.91705
1985	7.44744
1986	12.0897
1987	11.93729
1988	13.86707
1989	12.93454
1990	12.86089
1991	11.31781
1992	11.52756
1993	11.24852
1994	10.31394
1995	10.45257
1996	8.98669
1997	9.13919
1998	10.95557
1999	8.35576
2000	5.30425
2001	5.79993
2002	6.26158
2003	6.27522
2004	5.50941
2005	6.10424
2006	4.81315
2007	4.91981
2008	4.24815
2009	5.27993
2010	4.03853
2011	3.98394
2012	3.79877
2013	4.26008
2014	4.55766
2015	5.81058
2016	6.76366
2017	7.30994
2018	6.78839
2019	7.34699
2020	10.69043
2021	9.09675
2022	8.04192