Year	years
1970	4
1971	4
1972	4
1973	4
1974	4
1975	4
1976	4
1977	4
1978	4
1979	4
1980	4
1981	4
1982	4
1983	4
1984	4
1985	4
1986	4
1987	4
1988	4
1989	4
1990	4
1991	4
1992	4
1993	4
1994	4
1995	4
1996	4
1997	3
1998	3
1999	3
2000	3
2001	3
2002	3
2003	3
2004	3
2005	3
2006	3
2007	3
2008	3
2009	3
2010	3
2011	3
2012	3
2013	3
2014	4
2015	4
2016	4
2017	4
2018	4
2019	4
2020	4
2021	4
2022	4
2023	4