Year	Percent
1960	54.91924
1961	51.73853
1962	52.80199
1963	53.32618
1964	50.49702
1965	46.1467
1966	47.20252
1967	44.53125
1968	41.5873
1969	40.86758
1970	39.08397
1971	37.36082
1972	34.31339
1973	33.95604
1974	36.00242
1975	35.37077
1976	32.51944
1977	31.43993
1978	31.80353
1979	27.90756
1980	26.14614
1981	24.16276
1982	22.35375
1983	20.91501
1984	21.20143
1985	19.69056
1986	19.5126
1987	17.81847
1988	17.25896
1989	16.58598
1990	17.47623
1991	15.24708
1992	14.98367
1993	15.41602
1994	15.46283
1995	15.6932
1996	16.85456
1997	14.46115
1998	12.45032
1999	10.45783
2000	10.03285
2001	8.78804
2002	10.19076
2003	9.79515
2004	9.32742
2005	9.16534
2006	8.09488
2007	7.45703
2008	7.42467
2009	8.07199
2010	8.96693
2011	8.17396
2012	7.69488
2013	6.67611
2014	6.55724
2015	6.86838
2016	6.14229
2017	6.03863
2018	5.79162
2019	6.40176
2020	6.66994
2021	5.53375
2022	6.47693