Year	Number
1961	259.6467917843105
1962	267.0882859482199
1963	264.7933442480537
1964	268.759201195734
1965	271.18644067796606
1966	311.31726473350216
1967	312.344186099824
1968	297.7900552486188
1969	280.32592843102026
1970	279.2274882772141
1971	278.2502391835867
1972	277.5333919859234
1973	276.931301790965
1974	276.4490111115878
1975	274.572053713158
1976	272.9632330859325
1977	270.7020026587761
1978	264.3108791820084
1979	258.53619771661675
1980	250.37747344441206
1981	248.84109030224363
1982	248.66189119377947
1983	248.7684073176577
1984	249.03469762735332
1985	248.71514925571861
1986	251.91063297206614
1987	257.83075448740726
1988	244.8822560325613
1989	241.62448983987167
1990	238.40986449514205
1991	235.13011913225185
1992	233.86060408518037
1993	236.28023288900565
1994	238.04912635553674
1995	238.8986411055934
1996	243.40955051785974
1997	246.08343844317312
1998	249.7259336357774
1999	254.2747251494001
2000	256.8099653300488
2001	259.29789053591793
2002	265.50032663302056
2003	266.6176617878503
2004	267.71669616932286
2005	268.8932980334467
2006	270.10217326229554
2007	271.3445419705773