Year	Number
1960	20399
1961	29321
1962	29386
1963	30637
1964	32322
1965	33973
1966	35529
1967	37727
1968	39985
1969	40436
1970	38356
1971	36056
1972	36601
1973	39199
1974	43652
1975	-5357
1976	-10308
1977	-14695
1978	-14673
1979	-10236
1980	-3466
1981	10366
1982	19326
1983	29062
1984	30810
1985	31967
1986	32496
1987	32345
1988	30243
1989	20445
1990	6021
1991	-8569
1992	-13201
1993	-16383
1994	-18725
1995	-19736
1996	-20396
1997	-20588
1998	-20331
1999	-20220
2000	-22770
2001	-22787
2002	-22668
2003	-22353
2004	-22336
2005	-21961
2006	-19958
2007	-18051
2008	-12450
2009	-7869
2010	-4970
2011	-1011
2012	3127
2013	5369
2014	5801
2015	5522
2016	5215
2017	4926
2018	4690
2019	4478
2020	2344
2021	2344
2022	3886
2023	3718