Year	Percent
1961	36.39026
1962	36.40193
1963	36.43876
1964	36.4756
1965	36.51244
1966	36.51858
1967	36.56156
1968	36.59225
1969	36.63523
1970	36.65365
1971	36.93239
1972	37.32901
1973	37.74712
1974	37.42725
1975	37.10798
1976	36.80714
1977	36.64935
1978	36.14222
1979	36.78136
1980	35.4337
1981	35.78182
1982	36.14222
1983	36.35281
1984	36.55542
1985	37.06501
1986	37.26761
1987	37.47022
1988	37.98657
1989	37.88158
1990	37.75879
1991	38.67789
1992	39.16292
1993	39.38702
1994	39.39009
1995	39.4214
1996	39.55586
1997	39.19055
1998	39.77689
1999	39.10153
2000	38.60851
2001	39.18502
2002	39.32071
2003	39.4564
2004	39.59208
2005	29.24372
2006	29.37941
2007	29.51509
2008	28.66291
2009	28.66365
2010	28.57352
2011	28.48339
2012	28.39326
2013	28.2141
2014	28.2141
2015	28.2141
2016	28.2141
2017	28.61941
2018	28.91525
2019	28.96045
2020	28.98469
2021	29.00894