Year	Number
1996	4.98
1997	6.79
1998	4.95
1999	6.81
2000	6.33
2001	7.27
2002	6.9
2003	4.95
2004	6.39
2005	10.96
2006	7.28
2007	9.21
2008	3.94
2009	7.3
2010	5.23
2011	13.44
2012	12.99
2013	14.67
2014	12.19
2015	13.8
2016	14.1
2017	11.15
2018	16.72
2019	20.55
2020	20.9