Year	Percent
1970	65.33139
1971	64.76177
1972	60.77313
1973	63.31364
1974	61.03422
1975	61.3036
1976	59.47548
1977	55.58016
1978	53.96402
1979	53.83225
1980	57.57194
1981	58.1426
1982	52.61268
1983	53.48219
1984	54.65986
1985	55.95197
1986	52.51959
1987	50.55635
1988	48.21563
1989	47.12209
1990	51.05685
1991	48.59791
1992	48.00452
1993	47.16981
1994	40.73233
1995	42.02269
1996	53.38092
1997	42.42186
1998	44.5387
1999	47.6353
2000	44.10704
2001	43.84314
2002	43.33361
2003	42.84128
2004	41.9026
2005	40.84812
2006	40.63768
2007	34.93417
2008	38.00482
2009	36.72136
2010	38.43055
2011	36.70458
2012	35.42003
2013	38.3674
2014	34.95819
2015	30.6847
2016	31.54434
2017	28.54665
2018	29.0119
2019	28.84439
2020	28.62495
2021	28.66022
2022	27.56671