Year	Number
1960	4135
1961	4258
1962	4388
1963	4524
1964	4666
1965	4832
1966	5044
1967	5294
1968	5497
1969	5646
1970	5802
1971	5957
1972	6114
1973	6278
1974	6447
1975	6656
1976	6896
1977	7131
1978	7357
1979	7572
1980	7776
1981	7963
1982	8957
1983	10992
1984	13299
1985	15714
1986	18234
1987	20853
1988	23552
1989	26303
1990	28127
1991	28736
1992	29035
1993	29247
1994	29380
1995	29435
1996	29407
1997	29299
1998	29102
1999	29099
2000	29610
2001	30387
2002	31160
2003	31929
2004	32697
2005	33452
2006	34183
2007	34887
2008	35541
2009	36132
2010	36458
2011	36350
2012	36026
2013	35639
2014	35261
2015	35020
2016	34811
2017	34496
2018	33852
2019	33121
2020	32553
2021	31948
2022	31791
2023	32077