Year	Number
1971	346
1972	384
1973	492
1974	539
1975	586
1976	637
1977	787
1978	851
1979	961
1980	1202
1981	1284
1988	2035
1989	2443
1990	2644
1991	2775
1992	2894
1995	3119
1996	3548
1997	3579
1998	3621
1999	4303
2000	4537
2001	4589
2002	4165
2003	4406
2004	5131
2005	6633
2006	7358
2010	9945
2011	9873
2013	16406
2014	20509
2015	21296
2016	26839
2017	26456
2018	29225