Year	Number
1970	10928
1971	11487
1972	11895
1973	12274
1974	12668
1975	13119
1976	13636
1977	14208
1978	14776
1979	15318
1980	15784
1981	16220
1982	16784
1983	17289
1984	17816
1985	18327
1986	18674
1987	19195
1988	19574
1989	19915
1990	20300
1991	20554
1992	20829
1993	21126
1994	21391
1995	21577
1996	21560
1997	21435
1998	21103
1999	20779
2000	20344
2001	20127
2002	19872
2003	19771
2004	19694
2005	19693
2006	19700
2007	19676
2008	19633
2009	19682
2010	19568
2011	19340
2012	19214
2013	19275
2014	19311
2015	19565
2016	20020
2017	20373
2018	20701
2019	21021
2020	21307
2021	21513
2022	21710