1950: 67 percent and you can thirteen many years 1951: 65 percent and you will fifteen years 1952: 66 percent and 16 age 1953: 66 percent and fifteen years 1954: 67 percent and you will sixteen years 1955: seventy percent and you will 16 years 1956: 70 percent and you can 16 age 1957: 69 % and you will 17 ages 1958: 71 percent and you may 18 age 1959: 73 per cent and you may 19 age