Year Number 2004-01-01 521 2005-01-01 501 2006-01-01 491 2007-01-01 489 2008-01-01 492 2009-01-01 488 2010-01-01 492 2011-01-01 497 2012-01-01 498 2013-01-01 498 2014-01-01 461 2015-01-01 450