Year	Number of
1980	0
1981	2
1982	0
1983	1
1984	1
1985	4
1986	1
1987	0
1988	0
1989	2
1990	2
1991	3
1992	3
1993	2
1995	2
1996	0
1997	0
1998	3
1999	2
2000	5
2001	1
2002	0
2003	0
2004	1
2006	0
2007	1
2008	1
2009	2
2010	4
2011	2
2012	6
2013	5
2014	0
2015	7
2016	3
2017	4
2018	3
2019	4
2020	2