Year	Number of
1980	1
1981	2
1982	5
1983	10
1984	3
1985	3
1986	6
1987	2
1988	1
1989	2
1990	0
1991	3
1992	4
1995	4
1996	0
1997	4
1998	0
1999	0
2000	0
2001	0
2002	0
2004	6
2006	3
2010	1
2011	1
2012	3
2013	0
2014	0
2015	0
2016	2
2017	2
2018	2
2019	2
2020	3