Year	Number
1960	2.318239843754378
1961	2.3777922513196135
1962	2.67377174162742
1963	4.289157984073089
1964	3.7900120405316398
1965	2.1290582095174497
1966	3.1751845407668204
1967	4.089588537856987
1968	7.8970230176948935
1969	5.883594939186825
1970	3.3774458924803294
1971	2.247757669165431
1972	3.4311888490166123
1973	2.486945328331233
1974	1.7831308945258
1975	2.2827717916109647
1976	4.8063966202027295
1977	49.51800669935511
1978	20.371397952607815
1979	21.719013072005115
1980	6.300195935894528
1981	3.199607481333452
1982	1.9266881253664774
1983	3.2464760399213315
1984	3.088904688618373
1985	3.4811479321352863
1986	6.084786781497631
1987	44.25691059737011
1988	11.154428364787114
1989	20.279991392685258
1990	3.489385690350679
1991	3.061334309624954
1992	12.084446438438782
1993	117.73632483952908
1994	3.259923981277617
1995	4.69872762534638
1996	3.245335472043891
1997	2.8017069817807334
1998	40.78097546707355
1999	33.40996219888687
2000	3.834790362795219
2001	55.97251174750918
2002	5.755796745173028
2003	4.824860821942174
2004	2.6176536722938395
2005	2.3101962974513857
2006	1.6045296800100064
2007	1.7057679516533024
2008	1.2982047585898666
2009	1.2355064275031085
2010	1.627851718211352
2011	1.747519186089443
2012	1.6273336651011785
2013	1.4605582097234762
2014	1.7238408291003093
2015	1.9220145967437878
2016	4.344734925053544
2017	2.9953856176476137
2018	3.0477116865556404
2019	2.819947862483152