Year	Number
1996	2.17722582817078
1998	2.15422010421753
2000	2.0680627822876
2002	1.88889062404633
2003	1.78525233268738
2004	1.76227986812592
2005	1.74680650234222
2006	1.75363004207611
2007	1.80886840820313
2008	1.86873841285706
2009	1.77574038505554
2010	1.78359937667847
2011	1.7832305431366
2012	1.95790207386017
2013	1.96010839939117
2014	2.22636008262634
2015	2.25223541259766
2016	2.17064332962036
2017	2.10863542556763
2018	2.12173795700073
2019	2.15443754196167
2020	2.20529913902283
2021	2.22689867019653
2022	2.21437835693359