Year	Number
1999	21.17891
2000	19.4417
2001	19.23681
2002	19.11933
2003	18.10172
2004	17.78757
2005	17.2411
2006	17.29762
2007	14.69622
2008	14.8561
2009	14.51151
2010	14.04712
2011	13.22435
2012	12.93248
2013	12.70262
2014	12.74439
2015	12.13654
2016	11.91951
2017	11.91148
2018	11.64035