Year	Number
1960	2.6826545518134304
1961	2.7835905698501118
1962	2.6015120354742995
1963	3.2698019275200485
1964	3.3936649965984698
1965	2.95368716421348
1966	3.3907191583540133
1967	5.053313656902821
1968	3.7608360741775675
1969	2.3506226229372977
1970	1.9052194847821606
1971	1.995054126986272
1972	1.9042100421643098
1973	2.533237315473714
1974	2.1862869531614963
1975	2.008075525628685
1976	3.5814093509334626
1977	5.435822916349035
1978	9.0366253310433
1979	10.534818345294385
1980	4.5430020363422
1981	9.15950063012397
1982	8.420657692005078
1983	14.726188724898313
1984	13.06620178055849
1985	12.747811638574287
1986	5.274431273720812
1987	2.973811538347907
1988	2.8591661152265107
1989	2.483575545227936
1990	2.1975721881973196
1991	2.113411816017223
1992	2.6790644702212605
1993	2.974003292777148
1994	3.3221871682077997
1995	3.5375029627373444
1996	3.557896574924318
1997	4.5602556962493
1998	5.489487442326911
1999	4.637035782738603
2000	3.980508576335258
2001	4.275056921200983
2002	3.197264779609298
2003	3.3439613341888124
2004	3.958747062746248
2005	4.682656642507691
2006	5.000372201138521
2007	4.172337116305142
2008	5.367660495934108
2009	3.7947128313274585
2010	3.724369711887421
2011	4.010950880635143
2012	3.7672409079052547
2013	3.411442113584789
2014	3.3112134230062567
2015	2.9330774181258468
2016	2.7091481903542913
2017	2.530103772341358
2018	2.573850962065596
2019	2.304885149651958
2020	2.4525590064278897
2021	2.145258357887076
2022	2.341233534128984
2023	2.6354627497637653