Year	Number
1960	-463
1961	-523
1962	-630
1963	-558
1964	-416
1965	-206
1966	300
1967	740
1968	2158
1969	3301
1970	4818
1971	4276
1972	5230
1973	6733
1974	7976
1975	9117
1976	10254
1977	10741
1978	11566
1979	12398
1980	11762
1981	11830
1982	11415
1983	10716
1984	9307
1985	7892
1986	5998
1987	3333
1988	303
1989	-3043
1990	-7205
1991	-10338
1992	-13235
1993	-15569
1994	-18110
1995	-20394
1996	-22642
1997	-25088
1998	-27099
1999	-29076
2000	-31240
2001	-33177
2002	-33905
2003	-34848
2004	-35427
2005	-35453
2006	-34885
2007	-33813
2008	-32451
2009	-30706
2010	-28864
2011	-26445
2012	-24664
2013	-22781
2014	-20883
2015	-18912
2016	-17334
2017	-15937
2018	-14451
2019	-13398
2020	-12625
2021	-11853
2022	-15192
2023	-13128