Year	Number
1960	20233
1961	20557
1962	20863
1963	21171
1964	21485
1965	21792
1966	22068
1967	22304
1968	22509
1969	22693
1970	22953
1971	23301
1972	23642
1973	23966
1974	24277
1975	24581
1976	24898
1977	25252
1978	25679
1979	26153
1980	26624
1981	27107
1982	27607
1983	28086
1984	28513
1985	28886
1986	29239
1987	29608
1988	29984
1989	30360
1990	30280
1991	29690
1992	29019
1993	28305
1994	27589
1995	27359
1996	27616
1997	27865
1998	28083
1999	28296
2000	28615
2001	29046
2002	29479
2003	29928
2004	30439
2005	30793
2006	30920
2007	30958
2008	30891
2009	30780
2010	30699
2011	30642
2012	30562
2013	30408
2014	30189
2015	30271
2016	30625
2017	31006
2018	31434
2019	31836
2020	32241
2021	32489
2022	32582
2023	32671