Year	Number
2000	1400
2001	1400
2002	1600
2003	1600
2004	1700
2005	1700
2006	1700
2007	1700
2008	1800
2009	2100
2010	2200
2011	2300
2012	2400
2013	2500
2014	2500
2015	2500
2016	2600
2017	2600
2018	2500
2019	2400
2020	2500