Year	Number
1961	43.15152337960606
1962	46.19191795055136
1963	49.06188372426102
1964	51.781554242002784
1965	54.25243950983873
1966	56.09983688859703
1967	57.52979765797198
1968	58.750040332873844
1969	60.91762855293942
1970	63.3694755004139
1971	65.74062858682743
1972	66.6523739077263
1973	69.18539087852938
1974	69.8506891632463
1975	78.15631690835927
1976	78.33103105498591
1977	79.98919722142652
1978	82.64640521111681
1979	86.81434794045944
1980	89.4988130294276
1981	97.07851025935675
1982	97.12622395703015
1983	98.31532457317469
1984	99.99404565271473
1985	102.89235291082763
1986	109.52848399839745
1987	115.05532766017149
1988	120.8443291345243
1989	123.83277727418725
1990	127.14125809431113
1991	130.1150842277215
1992	131.59307008507318
1993	133.23529696965608
1994	134.84377011834314
1995	135.45679754243483