Year	Number
1993	3.1377245509
1994	2.9520958084
1995	2.7664670659
1996	2.6906187625
1997	5.6368330465
1998	5.4381812966
1999	5.2395295468
2000	5.0408777969
2001	4.875
2002	4.7091222031
2003	4.4401893287
2004	4.1712564544
2005	3.90232358
2006	3.4311531842
2007	2.9599827883
2008	2.8558519793
2009	2.7026678141
2010	2.584767642
2011	2.5520654045
2012	2.8627366609
2013	2.7426850258
2014	2.406626506
2015	2.4681583477
2016	2.3894148021
2017	2.3937177281
2018	2.3945783133
2019	2.4036144578
2020	2.3881239243