Year	Number
1961	32.78688524590164
1962	33.81147540983606
1963	34.83606557377049
1964	36.08247422680412
1965	37.5
1966	39.361702127659576
1967	47.82608695652174
1968	50.21834061135371
1969	52.74725274725275
1970	55.55555555555556
1971	54.13934426229508