Year	Number
1960	1.8637253430143195
1961	1.8410310498686162
1962	1.8044019189609748
1963	1.8687368361638053
1964	2.5163532885737525
1965	2.2608426103129466
1966	2.355683918710246
1967	2.917942153206805
1968	3.0886315111045057
1969	3.3668249400212638
1970	3.5666567520079973
1971	3.7509108551902735
1972	3.307534752415202
1973	2.4005999317009254
1974	1.7409790407505246
1975	1.906177638677667
1976	2.042607136645404
1977	3.063437449795897
1978	4.133309018170626
1979	3.1905870179251856
1980	4.045627953035608
1981	3.183113665605218
1982	4.684699877751211
1983	7.232421270847928
1984	15.001936551910664
1985	8.834829499252566
1986	6.408986505632086
1987	10.046034217600766
1988	16.6570152297765
1989	23.463514494564333
1990	62.706434721003454
1991	37.69409176811121
1992	12.643220389898342
1993	4.874109202794102
1994	3.773291065364861
1995	2.742904767609704
1996	2.8608798290438213
1997	4.77676358001688
1998	4.386766015456906
1999	5.003716719022696
2000	7.862702236194609
2001	6.244255143360124
2002	3.579312181082568
2003	4.049912162257117
2004	3.0697846661628594
2005	5.207053973713737
2006	7.484437116308018
2007	6.072221898813179
2008	10.56154438440944