Year	Number
1971	3799
1972	4179
1973	4536
1974	4918
1975	5371
1976	6198
1977	5950
1978	6626
1979	7164
1980	7590
1981	7784
1982	7806
1983	8164
1984	8509
1985	8785
1987	9485
1988	9843
1996	11852
1999	13228
2000	13579
2001	13953
2002	14296
2003	14578
2004	15165
2005	15432
2006	15754
2007	16444
2008	16791
2009	17146
2010	17347
2011	17608
2012	18525
2013	17757
2014	17520
2015	17453
2016	17262
2017	17431
2018	17488
2019	17316
2020	17533
2021	17729
2022	17656