Year	Number
1980	19612
1981	20808
1982	20530
1983	19893
1984	19093
1985	19672
1986	20040
1987	19945
1988	20536
1989	19732
1990	19310
1991	19230
1992	18848
1993	18727
1994	18384
1995	18630
1996	18184
1997	17938
1998	19530
1999	21333
2000	22050
2001	21423
2002	20624
2003	20426
2004	19178
2005	17833
2006	17484
2007	17375
2008	16523
2009	15985
2010	15490
2011	15343
2012	15370
2013	14972
2014	15196
2015	14867
2016	13876
2017	13301
2018	12865
2019	12061
2020	11990
2021	11592