Year	Percent
1960	27.64883
1961	27.15308
1962	24.62783
1963	24.42186
1964	23.19902
1965	25.69411
1966	24.88447
1967	24.15575
1968	25.38007
1969	25.54368
1970	24.10982
1971	22.93154
1972	23.74969
1973	26.57493
1974	28.80749
1975	27.66555
1976	26.01497
1977	24.81882
1978	23.39454
1979	20.05644
1980	16.58186
1981	21.62057
1982	18.04863
1983	19.04511
1984	18.10759
1985	17.10456
1986	17.39002
1987	19.63301
1988	18.04546
1989	18.6948
1990	18.51253
1991	16.98667
1992	15.58591
1993	15.73905
1994	15.71429
1995	15.71078
1996	16.11508
1997	15.75103
1998	15.88448
1999	15.90865
2000	15.53808
2001	15.35127
2002	15.40486
2003	15.28671
2004	14.26994
2005	13.98165
2006	13.2372
2007	13.42013
2008	12.63024
2009	12.99795
2010	13.34076
2011	13.86911
2012	11.27276
2013	11.27435
2014	11.33771
2015	11.39406
2016	11.76932
2017	10.98638
2018	10.83025
2019	10.69714
2020	11.16682
2021	11.43693
2022	10.94575