Year	Number
1960	1.182602859106924
1961	1.6901100893671255
1962	1.1704285627692812
1963	1.0823467512828242
1964	0.6510086062004062
1965	0.5637339704291199
1966	0.4833742618924267
1967	0.7766573947954734
1968	0.8424253917214047
1969	1.0659209651230739
1970	1.3987020167826307
1971	1.9463858439321884
1972	3.1509184371158026
1973	2.021660556467379
1974	1.3287034594821392
1975	1.5360881465790548
1976	1.8261672693198223
1977	1.3227139639777667
1978	1.427002398766492
1979	0.690508528751025
1980	0.6545402023652949
1981	0.9436558933138375
1982	1.9574061828896627
1983	2.3463285885740373
1984	3.2141930404242967
1985	4.121298485783526
1986	4.8576693977566086
1987	2.7381492515252392
1988	2.6074428974056376
1989	1.3654806522190384
1990	1.440558243660106
1991	1.851209618914704
1992	2.0688238418874434
1993	2.163309143531295
1994	2.381119760202601
1995	2.458669969712645
1996	6.249855561230535
1997	4.334762799851624
1998	4.579283431357556
1999	6.569905778989244
2000	9.781954740638882
2001	4.535707574524708
2002	3.431879811697777
2003	3.305411026079377
2004	3.1327815449678544
2005	2.907139444225185
2006	2.0999982951056553
2007	1.1546067942359315
2008	1.4001777415603824
2009	1.3012632645448958
2010	1.9317080175236034
2011	2.1544116063761374
2012	2.5813912607942053
2013	2.508493288746191
2014	5.750893533811154
2015	6.016074179989232
2016	6.437639226493282
2017	6.753619440446915
2018	6.5572972680694415
2019	7.231343700751771
2020	7.12847382807435