Year	Number
1971	434370
1972	485955
1973	516131
1974	576420
1980	1420839
1981	1300673
1982	1258858
1983	1178430
1984	1065025
1985	870410
1986	974498
1987	1012303
1988	1031314
1989	1067906
1990	1041126
1991	990155
1992	989444
1998	1342116
2007	3558605
2008	3930051
2009	4046266
2010	4273006
2011	5026803
2015	5620915
2016	5259091
2017	6246294
2018	4697461