Year	Number
1996	10.65366
1999	15.79817
2009	23.51859
2011	21.99714
2012	20.04527
2013	19.53378
2014	19.74006
2015	17.14638
2016	18.11717
2017	16.55454
2018	21.21135
2019	22.64559