Year	Number
1996	2.03140759468079
1998	2.0342104434967
2000	2.04931902885437
2002	1.98223149776459
2003	1.93129205703735
2004	1.80586624145508
2005	1.86970067024231
2006	1.95279455184937
2007	1.99088037014008
2008	1.98772144317627
2009	2.05179667472839
2010	2.06187319755554
2011	1.97113347053528
2012	1.91890442371368
2013	1.87934255599976
2014	1.83242726325989
2015	1.84586489200592
2016	1.94443845748901
2017	1.88070380687714
2018	1.78985774517059
2019	1.72997653484344
2020	1.5655562877655
2021	1.61652982234955
2022	1.65857982635498