Year	Number
1971	26787
1972	27531
1973	27977
1974	27585
1975	29724
1976	29025
1977	28677
1978	30021
1979	29446
1980	29816
1981	28818
1982	27787
1983	27640
1984	27715
1985	28695
1989	25422
1990	24004
1999	21841
2000	21016
2001	20752
2002	20762
2003	20838
2004	21222
2005	21345
2006	20855
2007	20651
2008	20337
2009	19928
2010	19497
2011	19696
2014	20603
2015	20554
2016	20370
2017	20249
2018	19571