Year	Number
1960	2.5538148612071376
1961	2.7355049723054337
1962	2.7683447118502142
1963	2.5183137556217674
1964	2.0173945108687916
1965	2.142531895020111
1966	2.255129791091467
1967	2.281923805847541
1968	2.18221716469844
1969	2.5897708649411193
1970	2.4932316959951795
1971	1.9663676876091678
1972	1.835046188592909
1973	1.429557361373547
1974	0.7626692402155378
1975	0.9520116255857412
1976	1.2155913255675264
1977	1.531629231504958
1978	1.9704779477224836
1979	1.382687826011748
1980	1.6010332723369742
1981	1.9077329051602208
1982	2.2294035981579143
1983	2.709636079244896
1984	1.8974533542562482
1985	1.7291478015669606
1986	2.323030660137887
1987	1.456487485435392
1988	2.589691986933571
1989	1.3758214668479882
1990	1.146975635162056
1991	1.208126872187985
1992	1.3001604320749047
1993	1.2008407296444827
1994	1.3634626116433446
1995	1.818052558882517
1996	0.8699172752043546
1997	1.0456864416902605
1998	1.2043613744255877
1999	1.2912618284010555
2000	1.4619999026177286
2001	1.9719923692517987
2002	1.4276008743192263
2003	0.9749865985916151
2004	1.103666009394041
2005	1.1567311087402212
2006	1.5786724188516001
2007	2.2988166638220493
2008	2.3236582818505007
2009	3.596285696817563
2010	4.262404089360876
2011	4.071961649540972
2012	5.916947096507311
2013	9.679430448210551