Year	Number
1977	6.045427078645619
1978	6.562678220398305
1979	8.179383289794927
1980	6.979406898853963
1981	4.658355487013074
1982	5.384077402026987
1983	5.851748803112674
1984	5.3190356184892345
1985	5.392251446795312
1986	5.40833797790883
1987	5.7179266207664385
1988	4.335143337225792
1989	4.357281130838626
1990	5.529422509039478
1991	6.099143887302058
1992	5.399854267565272
1993	5.759318500190253
1994	6.090738816754494
1995	5.649327736272967
1996	6.336711774692063
1997	8.073054885688265
1998	8.323779637535237
1999	7.942828121798404
2000	7.1027299053490465
2001	7.977989435010184
2002	9.438156593187289
2003	8.942906423611063
2004	9.656764075777133
2005	10.767824175704021
2006	12.28651931194425
2007	14.368275303933343
2008	14.076573158790396
2009	18.782673901606174
2010	16.600520131608317
2011	15.593967824939812
2012	14.918755322649867
2013	15.125260719332488
2014	14.535436418170757
2015	14.37922953934929
2016	13.949910487954632
2017	12.826009751937024
2018	11.21626773137594
2019	11.4842315341767
2020	13.571978695641542
2021	10.520005780299249
2022	9.431805284183564
2023	10.176937390350284