Year	Number
1961	42.3806337743837
1962	45.040393796789004
1963	47.669144187197105
1964	50.29639418538795
1965	52.52184796451627
1966	54.12218684224729
1967	55.55309262969436
1968	56.81154560828444
1969	57.71408866193315
1970	59.23157453336743
1971	61.39225009206596
1972	63.169646894230475
1973	65.36309079819624
1974	66.06860340038376
1975	74.61762556899212
1976	75.57346983269349
1977	75.94752153286352
1978	78.49781910115482
1979	82.48353574649255
1980	85.53265991291245
1981	93.58209332773917
1982	93.697130620985
1983	95.0495024406896
1984	96.83949562588205
1985	99.68845438186787
1986	106.11345579212134
1987	111.79968630754882
1988	117.73879076115789
1989	120.66886888113865
1990	124.10259836752546
1991	127.20224621304156
1992	128.8832050089307
1993	130.59607236072986
1994	132.3038108530103
1995	132.93554034972857
1996	135.71598773436534
1997	134.68524658450372
1998	135.86552055025308