Year	Number
1992	4.547099189
1993	5.05154398
1994	5.5559887711
1995	6.0604335621
1996	6.5648783531
1997	7.0693231441
1998	7.5737679351
1999	8.0782127261
2000	8.5826575172
2001	9.5086712414
2002	10.4346849657
2003	11.36069869
2004	12.28621335
2005	13.2127261385
2006	12.0013793581
2007	10.7900325778
2008	9.5786857975
2009	8.3673390171
2010	7.1559922368
2011	5.9446454564
2012	4.7332986761
2013	3.5219518958
2014	2.3106051154
2015	2.3562071117
2016	2.3462258266
2017	2.4248284467
2018	2.4067373674
2019	2.4273237679
2020	2.4273237679