Year	Percent
1961	52.35919
1962	52.82968
1963	53.4346
1964	54.01712
1965	54.71165
1966	55.42412
1967	55.87221
1968	56.54434
1969	56.97226
1970	57.59063
1971	58.10145
1972	58.63243
1973	59.20905
1974	59.66838
1975	60.31145
1976	60.83352
1977	61.61775
1978	62.55434
1979	62.74703
1980	64.82187
1981	65.18037
1982	65.37531
1983	65.59041
1984	65.83912
1985	65.87049
1986	66.09231
1987	66.47098
1988	66.64575
1989	67.36276
1990	67.9879
1991	68.01479
1992	68.5996
1993	68.81246
1994	69.37934
1995	68.8976
1996	69.38382
1997	69.22474
1998	69.40623
1999	68.77213
2000	68.68026
2001	68.0484
2002	67.85346
2003	69.18216
2004	67.31123
2005	67.19471
2006	67.09836
2007	67.12973
2008	67.17679
2009	67.22518
2010	67.19314
2011	67.45194
2012	68.12234
2013	68.53014
2014	67.40421
2015	67.32467
2016	69.17992
2017	69.5643
2018	68.39751
2019	66.34978
2020	68.02151
2021	67.87139