Year	Number
1990	15
1991	15
1992	15
1993	15
1994	15
1995	15
1996	15
1997	15
1998	15
1999	15
2000	15
2001	15
2002	15
2003	15
2004	15
2005	15
2006	15
2007	15
2008	16
2009	17
2010	17
2011	17
2012	19
2013	19
2014	21
2015	21
2016	21
2017	21
2018	21
2019	21
2020	23
2021	21
2022	21