Year	Number
1996	21.2765960693359
1998	22.8723411560059
2000	20.1058197021484
2002	17.4603176116943
2003	21.1055278778076
2004	16.990291595459
2005	16.990291595459
2006	16.425121307373
2007	25.6038646697998
2008	32.6923065185547
2009	35.5450248718262
2010	36.4928894042969
2011	29.8578205108643
2012	23.222749710083
2013	33.6492881774902
2014	26.1904754638672
2015	21.9047622680664
2016	18.0952377319336
2017	19.5238094329834
2018	20.7547168731689
2019	22.6415100097656
2020	17.4528293609619
2021	18.3962268829346
2022	15.5660381317139