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