Year	Number
1999	31.11996
2000	32.39259
2001	32.15692
2002	30.79429
2003	35.24926
2004	40.68392
2005	37.96515
2006	35.15157
2007	36.00575
2008	36.88614
2009	37.95467
2010	37.07354
2011	38.31964
2013	31.34883
2014	29.54108
2015	28.69143
2016	25.34081
2017	20.20097
2018	29.72838