Year	Number
1971	19163
1972	19499
1973	19831
1974	20086
1976	21339
1977	21297
1978	21273
1979	20063
1981	22277
1982	17306
1984	16728
1987	16169
1988	16057
1989	16154
1990	17729
1991	18960
1992	19583
1994	19443
1996	18146
1997	19523
1998	18654
1999	19739
2000	19490
2001	20368
2002	20363
2003	20053
2004	21562
2005	21681
2006	22083
2007	22257
2008	22730
2009	23800
2010	24053
2011	23872
2012	23829
2014	25071.830078125
2015	25406.92578125
2016	25787.17578125
2017	25761.830078125
2018	26126.47265625
2019	26808.5703125
2020	26684.94921875
2021	26607.22265625