Year	Number
1960	1.427345236977915
1961	1.3929446622704627
1962	1.4557485573130915
1963	0.9950331999888247
1964	0.8416836474432363
1965	1.158595117697478
1966	1.621977450265889
1967	1.7023032256505153
1968	1.1834491765590858
1969	1.0877314232211053
1970	0.9659253692283171
1971	1.0601042954996762
1972	1.1822556465053746
1973	1.2132069810411676
1974	1.2573701507125268
1975	1.802000887515726
1976	1.5976316361429337
1977	1.6649286874907905
1978	1.8339721123748445
1979	1.651372151210526
1980	1.678960799124558
1981	2.073394354661158
1982	2.271706554119655
1983	3.594765312446601
1984	5.465546048508378
1985	6.885899643020123
1986	5.404473312895448
1987	3.4749571129747925
1988	3.6956345599424854
1989	4.035459729960882
1990	3.2796426602329
1991	2.853830277664934
1992	2.1037802304998223
1993	1.8220390117799632
1994	1.9595375876339673
1995	2.593122441575393
1996	2.706541263678839
1997	3.1683253332224854
1998	2.7173264243314748
1999	2.7123155422884495
2000	2.856715540318365
2001	2.866024996931621
2002	2.874577100462683
2003	2.573762668439544
2004	2.5798317922891583
2005	2.8152865945779855
2006	2.669692604026904
2007	3.1202024830626316
2008	3.848496034445359
2009	3.677728609953799
2010	3.903351775597348
2011	3.874231934214251
2012	3.3267929086077053
2013	3.03080872318867
2014	2.755784832882996
2015	2.5833957328374635
2016	2.6450421966105155
2017	2.745239852384679
2018	3.7869245455794927
2019	3.812468310363073
2020	3.4329125178162108
2021	4.622165045038757
2022	5.0198737861164275
2023	3.966944917276737