Year	Number of
1980	8
1981	2
1982	12
1983	15
1984	3
1985	8
1986	3
1987	2
1988	0
1989	2
1990	0
1991	1
1992	6
1993	5
1994	4
1995	2
1996	1
1997	2
1998	0
1999	3
2000	1
2001	2
2002	1
2003	0
2004	1
2005	1
2006	1
2008	2
2009	2
2010	0
2011	1
2012	1
2013	2
2014	2
2015	0
2016	2
2017	0
2018	0
2019	1
2020	1