Year	Number
1996	4.23
1997	4.04
1998	2.14
1999	4.79
2000	2.95
2001	8.39
2002	13.78
2003	6.68
2004	18.14
2005	14.77
2006	19.24
2007	14.88
2008	20.19
2009	15.24
2010	20.07
2011	17.51
2012	19.87
2013	15.39
2014	18.89
2015	24.12
2016	29.68
2017	26.67
2018	40.45
2019	23.9
2020	16.97