Year	Number
1980	12129
1981	12118
1982	12097
1986	14546
1987	15412
1989	15831
1991	16445
1992	17691
1993	18634
1994	19593
1995	20101
1996	20855
1997	21159
1999	21659
2000	23235
2001	23431
2003	26810
2004	27904
2005	27925
2006	28460
2007	29182
2008	29807
2009	30405
2010	31458
2011	32103
2012	33671
2013	35574
2014	35877
2015	36045
2016	37305
2017	36524
2018	37052