Year	Number of
2000	3300
2001	3200
2002	3100
2003	3000
2004	2900
2005	2700
2006	2700
2007	2800
2008	2600
2009	2300
2010	2300
2011	2100
2012	2100
2013	2000
2014	2000
2015	1900
2016	1900
2017	2000
2018	1800
2019	2300
2020	2400