Year	Number
1961	30.47232097511427
1962	33.9446123276897
1963	37.67164904605663
1964	40.84708121827411
1965	44.28044280442804
1966	47.19494557357083
1967	50.18094989366861
1968	53.051368359432175
1969	55.77689243027888
1970	58.80663688576898
1971	62.56606089535954
1972	66.00551687902274
1973	69.20250839298157
1974	72.17787564608373
1975	95.53338063982024
1976	95.71471545382448
1977	94.12123833023836
1978	101.76906981167966
1979	108.25892857142858
1980	114.66845053132313
1981	117.21566446243537
1982	119.70125151392814
1983	122.0887666462196
1984	124.38390189001436
1985	125.93798480058868
1986	131.0582306830907
1987	136.40161007083523
1988	141.98761272620897
1989	147.82783671110744
1990	153.94571187156737
1991	160.3582399515424
1992	167.0839890940527
1993	174.153958044501
1994	181.5869980879541
1995	185.90042995089632
1996	186.31015299026424
1997	183.4922341423245
1998	180.74773106967083
1999	178.07381159323396
2000	175.46778736138003
2001	172.92732210755025
2002	170.44955152139394
2003	168.03238729095574
2004	165.6736326325488
2005	163.37119566341838
2006	161.10990718403727