Year	Number
1961	13.979408110999618
1962	14.999919443807379
1963	16.067091902083956
1964	17.16107816960406
1965	18.294444962290083
1966	19.926962253393988
1967	21.46334604229639
1968	23.075988361982525
1969	24.66819819183203
1970	25.36980054890557
1971	27.667269780420376
1972	30.4131146372387
1973	33.16930894676229
1974	36.22654538292471
1975	40.64185273176504
1976	43.740269514359404
1977	47.75263606790351
1978	52.3295948807804
1979	57.316308600061106
1980	60.84077632259731
1981	65.58803354950722
1982	67.6382057129461
1983	70.25461328720925
1984	72.43595189094944
1985	75.41892134075007
1986	78.90340303178289
1987	82.02290579742416
1988	85.20587440434741
1989	88.83806656733874
1990	90.9793083038152
1991	92.27105549322488
1992	99.16405191223296
1993	99.5423565768221
1994	101.33692432783366
1995	102.08478491597573
1996	103.13654064001916
1997	104.75241645159387
1998	106.56261647413699