Year	Percent
1961	45.80808
1962	45.85017
1963	45.89226
1964	45.93519
1965	45.97727
1966	46.01852
1967	46.06481
1968	46.10564
1969	46.14773
1970	46.18897
1971	46.23022
1972	46.27146
1973	46.3165
1974	46.34049
1975	46.38258
1976	46.42256
1977	46.4638
1978	46.4798
1979	46.47938
1980	46.48569
1981	46.49832
1982	46.52357
1983	46.54461
1984	46.56776
1985	47.43266
1986	48.71633
1987	49.58123
1988	50.86069
1989	51.70875
1990	51.7298
1991	51.75295
1992	52.19487
1993	53.3388
1994	53.92045
1995	54.56397
1996	54.94066
1997	55.06397
1998	55.17761
1999	55.28283
2000	55.37668
2001	55.5947
2002	55.81397
2003	56.62037
2004	56.60648
2005	56.91077
2006	57.26136
2007	57.4979
2008	57.53283
2009	57.7718
2010	57.76355
2011	57.76355
2012	59.67128
2013	59.66454
2014	59.66004
2015	59.82328
2016	59.98651
2017	60.14974
2018	60.31298
2019	60.31298
2020	60.31308
2021	60.31308