Year	Number
1997	10.72167383014717
1998	5.939007073851988
1999	2.8005934350810184
2000	2.4544275855913407
2001	1.7069096156127603
2002	1.8261782611269293
2003	1.7488585238493901
2004	1.7868122583573658
2005	2.0154024520466174
2006	1.7300651912344587
2007	1.6590803198422082
2008	2.079646555856154
2009	1.9730756994753085
2010	2.0919327577369415
2011	2.4125362329555
2012	2.2311611966753286
2013	2.1920810527892303
2014	2.4102578002411628
2015	2.2070670520548337
2016	2.2239350867623453
2017	1.9686564903060044
2018	2.1443191311357244
2019	2.091145768984444
2020	1.8895821954328982
2021	2.011463038665053
2022	2.0404073079409777
2023	2.1491379417388288