Year	Number
1997	700
1998	600
1999	700
2000	800
2001	900
2002	800
2003	600
2004	600
2005	800
2006	1100
2007	1100
2008	1000
2009	900
2010	1000
2011	1200
2012	1200
2013	1300
2014	1500
2015	1300
2016	1200
2017	1300
2018	1500
2019	1600
2020	1300