Year	Number
1975	4.110891266806983
1976	3.6393890686100754
1977	4.506458662450632
1978	5.2495347428103925
1979	6.797712019198898
1980	6.278058053719451
1981	4.668061594524705
1982	5.383949477318012
1983	4.911113529392525
1984	4.251571361757547
1985	4.5392272318484945
1986	4.386767617937757
1987	4.738547249271327
1988	3.787754499549369
1989	3.7451262032388435
1990	3.5253151333757287
1991	3.5954485215410554
1992	3.1807428159929922
1993	3.543987608933087
1994	3.4630804495934853
1995	3.1018671319588904
1996	3.6045374901402596
1997	3.5724428873754697
1998	3.82895809249246
1999	4.402596333618846
2000	4.561718607821856
2001	5.405553543151783
2002	6.327275855437168
2003	8.317830491682244
2004	9.07538220009042
2005	7.9922094131332075
2006	7.426992358523417
2007	7.17732651263843
2008	6.4250031327509385
2009	8.407050025848354
2010	7.349458185702
2011	7.175238295795541
2012	7.312938488534602
2013	7.628984594533326
2014	7.419143826476492
2015	8.817145406922135
2016	9.06800688275267
2017	9.151963401910697
2018	8.244049234695252
2019	8.765646488019712
2020	10.98410917031331
2021	9.32014266088327
2022	7.052064964869906
2023	6.892205118318359