Year	Percent
1960	23.57779
1961	23.85436
1962	23.45901
1963	24.46067
1964	21.95268
1965	21.57241
1966	19.08436
1967	18.83376
1968	17.3667
1969	17.9302
1970	16.82226
1971	18.02872
1972	17.38695
1973	16.48573
1974	27.66314
1975	28.74947
1976	20.77282
1977	18.74278
1978	20.24138
1979	19.8703
1980	20.68966
1981	18.78522
1982	20.19364
1983	19.82289
1984	20.8659
1985	22.51282
1986	22.58065
1987	25.8705
1988	22.61962
1989	35.06293
1990	38.12959
1991	40.52251
1992	43.79467
1993	36.67884
1994	37.95035
1995	40.85826
1996	37.76896
1997	36.35332
1998	33.90585
1999	35.01395
2000	29.98323
2001	29.73738
2002	30.88166
2003	32.11281
2004	31.49373
2005	28.88587
2006	34.00027
2007	30.38474
2008	31.72756
2009	29.42412
2010	28.52843
2011	25.6836
2012	25.44001
2013	25.64757
2014	24.59409
2015	25.44312
2016	20.38724
2017	22.75803
2018	19.53569
2019	17.59534
2020	16.851
2021	13.45519
2022	10.02984