Year	Number
1961	2.058212463787907
1962	2.3238705294317463
1963	2.6245034103580274
1964	2.852650407755039
1965	3.0627482432019555
1966	3.5207848401330915
1967	4.267981153140197
1968	5.053248111123201
1969	5.899127301498029
1970	6.544678024011769
1971	8.848374383296276
1972	10.429421324235197
1973	11.021489674404583
1974	12.090425582075197
1975	13.372521000108115
1976	15.077935817562008
1977	17.74313693257873
1978	20.184940185592367
1979	22.811200081983632
1980	23.377686891455394
1981	25.716892462630497
1982	27.8754053362617
1983	30.424722457151816
1984	33.297517313399
1985	35.861247516988776
1986	39.113816521253476
1987	42.22725310620231
1988	46.05560602042793
1989	55.02018720404418
1990	59.200377035390254
1991	63.11220892519718
1992	67.54800047068319
1993	69.71149165975939
1994	72.14074192881431
1995	79.47970520294797
1996	87.63881649255845
1997	94.77976713532513
1998	102.3537671114528
1999	110.21139429288571
2000	116.17823560435801
2001	124.09611713800179
2002	131.70666907903194
2003	139.73445073180048
2004	88.51786483879575
2005	93.41154076924668
2006	97.62402051015074