Year	Number
1970	4200
1971	4400
1972	4100
1973	4500
1974	5600
1975	7000
1976	8700
1977	9300
1978	10400
1979	11900
1980	14000
1981	16500
1982	17100
1983	16200
1984	15500
1985	15200
1986	14800
1987	15000
1988	15500
1989	17400
1990	14100
1991	11000
1992	14300
1993	15500
1994	16000
1995	16800
1996	17100
1997	16700
1998	15400
1999	15900
2000	16447
2001	15893
2002	16369
2003	15354
2004	17958
2005	19689
2006	26546
2007	29415
2008	30804
2009	32490
2010	39318.7915976253
2011	40329.1978021978
2012	39468
2013	38998
2014	38386
2015	36622
2016	38161
2017	36946
2018	36127
2019	36550
2020	10108
2021	19200