Year	Number
1971	20995
1972	22881
1973	23837
1974	25021
1975	25668
1976	25831
1977	23058
1978	21251
1979	20262
1980	18822
1981	14969
1982	13490
1983	12403
1984	12897
1985	12115
1986	13664
1992	35912
1993	34752
1996	30014
1998	29177
1999	19069
2000	23187
2001	24149
2002	27184
2003	26522
2004	28864
2005	34011
2006	30099
2007	31994
2008	39427
2010	43197
2011	45545
2012	44401
2013	51822
2014	50097
2015	47256
2016	45827
2017	43271