Year	Percent
1960	54.88213
1961	55.16128
1962	53.39505
1963	51.85181
1964	48.89431
1965	44.66232
1966	43.87946
1967	44.21053
1968	44.5743
1969	42.95982
1970	33.76072
1971	31.68569
1972	30.73285
1973	32.00884
1974	24.61082
1975	26.6062
1976	32.2973
1977	35.44503
1978	24.08602
1979	25.35583
1980	27.48855
1981	28.18356
1982	26.96297
1983	34.47567
1984	33.4608
1985	33.66423
1986	34.75776
1987	33.48428
1988	33.57476
1989	32.22346
1990	33.75411
1991	32.82417
1992	35.26325
1993	44.14365
1994	34.92288
1995	37.76285
1996	40.8371
1997	42.19239
1998	34.96374
1999	36.93322
2000	30.56164
2001	33.92963
2002	33.15439
2003	28.3791
2004	31.11189
2005	36.55006
2006	33.64337
2007	16.92978
2008	20.68167
2009	21.34835
2010	21.0778
2011	19.86497
2012	20.97595
2013	19.13955
2014	19.33884
2015	18.92186
2016	20.38508
2017	20.31556
2018	19.64948
2019	19.51459
2020	19.17252
2021	18.81445
2022	18.34999