Year	Number
1997	1
1998	2
1999	1
2000	1
2001	1
2002	1
2003	1
2004	1
2005	1
2006	1
2007	2
2008	2
2009	2
2010	2
2011	5
2012	3
2015	6
2018	4
2019	4
2020	4