Year	Number
1960	4.970508062156377
1961	14.008799831539749
1962	7.1008246086177635
1963	3.7529594766158456
1964	3.5586398173650036
1965	3.8520025060841805
1966	3.7922044342935943
1967	4.98840479597375
1968	5.626543363330516
1969	5.935139803953077
1970	8.93893762011417
1971	6.4398932101291235
1972	7.563072419616372
1973	6.374917247642788
1974	8.233481651400188
1975	8.245720481753978
1976	7.874804083528872
1977	6.3615297266851805
1978	7.2806349183803025
1979	4.9752900428463604
1980	5.916577218129591
1981	6.5035342724966805
1982	12.041916802454889
1983	11.959906618654601
1984	11.491971519793731
1985	3.348381010075743
1986	5.196221200055025
1987	9.16546453261534
1988	6.070443512908774
1989	11.69711769668959
1990	30.001105250096458
1991	4.212832469416669
1992	4.766222659052282
1993	4.379823372856985
1994	12.286220200399905
1995	9.768959119914852
1996	11.918780374123102
1997	12.272237939973301
1998	10.753651392495733
1999	8.82720531309446
2000	11.160635412510619
2001	8.518573817110655
2002	19.836743877871612
2003	37.77159333758873
2004	10.350429645854604
2005	6.593627320992505
2006	5.3887744382315645
2007	4.735489655177253
2008	5.418884269598711
2009	4.444536176529369
2010	4.507238658099717
2011	4.618970514771099
2012	5.687831991782142
2013	4.535229583312725
2014	4.59816537342485
2015	4.601282538590112
2016	4.239380489713419
2017	4.022794724282779
2018	3.6678418398546015
2019	3.4393157662669696
2020	3.1083404379116595
2021	2.884830404773181
2022	2.856058188051777
2023	2.9954525540613615