Year	Number
1999	11.35415
2000	11.13046
2001	11.66956
2002	11.55871
2003	12.54575
2004	13.03261
2005	14.27484
2006	15.109
2007	16.01882
2008	18.68097
2009	18.69061
2010	17.58989
2011	17.30161
2012	17.16668
2013	16.32972
2014	15.45976
2015	14.4427
2016	13.46318
2017	12.78663