Year	Number
1971	27066
1972	27336
1973	27217
1974	27046
1975	26922
1976	26418
1977	25924
1978	25138
1979	24687
1980	24599
1981	24736
1982	24809
1983	25018
1984	25280
1985	25058
1986	24603
1987	24560
1988	25108
1989	25420
1990	25525
1991	29816
1992	29649
1993	29351
1994	28960
1995	29138
1996	29221
1997	29342
1998	29705
1999	30355
2000	31282
2001	31786
2002	31465
2003	31470
2004	30984
2005	30785
2006	30421
2007	30084
2008	29945
2009	29860
2010	29568
2011	29432
2012	29387
2013	29578
2014	29892
2015	30422
2016	31194
2017	31981
2018	32421
2019	32811
2020	32832
2021	33023