Year	Number
1971	2435
1972	2980
1973	3282
1974	3590
1975	4108
1976	4564
1977	5433
1978	5890
1979	6388
1980	6971
1981	7607
1982	8215
1983	8536
1984	8664
1985	9249
1986	9726
1987	9917
1988	10340
1989	10925
1990	11384
1992	7963
1993	8517
1994	9294
1995	9850
1997	10860
1998	11780
1999	12387
2000	12277
2001	12911
2004	13606
2007	13926
2008	14999
2009	16900
2015	21883
2016	23289
2017	24467
2018	25681
2019	26283
2021	27159