Year	Number
1998	4.695307171876018
1999	5.204366529976251
2000	4.922449164437988
2001	5.456856720195058
2002	5.437915654155047
2003	5.295683631163348
2004	4.662232175559817
2005	4.088739059761884
2006	3.8320807932604017
2007	3.8100198719323464
2008	4.297186098811767
2009	6.680116327581613
2010	5.649477355461646
2011	5.278639769918457
2012	5.433076879283228
2013	4.934231360639027
2014	5.07732062272674
2015	5.683745218554597
2016	6.189910878322338
2017	6.400236552841087
2018	5.837146542962012
2019	6.3450978060361845
2020	7.560331671751987
2021	6.466762186988601
2022	5.71713130780848
2023	5.689590404689267