Year	Percent
1961	49.03934
1962	47.38422
1963	44.03409
1964	42.55319
1965	41.58802
1966	41.33486
1967	41.96246
1968	42.89011
1969	41.81229
1970	37.17904
1971	34.48549
1972	32.38043
1973	28.20597
1974	27.99571
1975	29.70183
1976	31.70366
1977	32.98421
1978	36.02722
1979	33.8601
1980	33.11866
1981	33.3928
1982	32.42625
1983	32.67678
1984	37.36757
1985	33.76511
1986	32.18909
1987	29.86371
1988	29.14735
1989	28.11505
1990	28.97406
1991	25.97903
1992	24.47312
1993	27.56672
1994	32.36352
1995	33.81278
1996	31.64525
1997	35.03305
1998	33.69214
1999	34.25727
2000	33.96639
2001	34.41128
2002	37.99065
2003	38.34859
2004	35.96866
2006	20.40324
2007	19.60859
2008	20.17487
2009	21.64347
2010	19.60839
2011	19.19971
2012	19.27395
2013	19.26002
2014	17.69194
2015	17.45693
2016	17.86634
2017	17.64957
2018	16.97384
2019	16.97614
2020	18.75533
2021	18.98994
2022	16.93195