Year	Number
1996	18.5
1998	13.4328355789185
2000	9.45273590087891
2002	5.47263669967651
2003	3.98009943962097
2004	2.4038462638855
2005	1.92307686805725
2006	6.73076915740967
2007	4.32692289352417
2008	4.32692289352417
2009	3.79146909713745
2010	5.68720388412476
2011	5.16431903839111
2012	3.75586843490601
2013	5.16431903839111
2014	7.38916254043579
2015	9.85221672058105
2016	9.85221672058105
2017	10.837438583374
2018	12.1359224319458
2019	12.0772943496704
2020	13.043478012085
2021	12.5603866577148
2022	13.043478012085