Year	Percent
1948	29.00
1949	29.83
1950	30.66
1951	31.52
1952	32.40
1953	33.31
1954	34.25
1955	35.21
1956	36.19
1957	37.20
1958	38.22
1959	39.26
1960	40.31
1961	41.37
1962	42.45
1963	43.53
1964	44.63
1965	45.48
1966	46.37
1967	47.27
1968	48.16
1969	49.05
1970	49.93
1971	50.81
1972	51.68
1973	52.53
1974	53.38
1975	54.22
1976	55.04
1977	55.84
1978	56.64
1979	57.41
1980	58.17
1981	58.91
1982	59.63
1983	60.33
1984	61.01
1985	61.67
1986	62.31
1987	62.93
1988	63.53
1989	64.11
1990	64.66
1991	65.20
1992	65.72
1993	66.21
1994	66.69
1995	67.14
1996	67.58
1997	68.00
1998	68.39
1999	68.77
2000	69.14
2001	69.03
2002	69.21
2003	68.46
2004	68.92
2005	68.91
2006	68.22
2007	67.76
2008	67.10
2009	66.14
2010	65.41
2011	64.75
2012	63.97
2013	63.39
2014	63.00
2015	62.64
2016	62.63
2017	63.09
2018	63.62
2019	63.91
2020	63.95
2021	63.96
2022	64.39
2023	65.00