Year Number 1960 0 1965 0 1970 0 1975 0 1976 0 1977 0 1978 0 1979 0 1980 0 1981 0 1982 0 1983 0 1984 0 1985 0 1986 0 1987 0 1988 0 1989 0 1990 0 1991 0 1992 0 1993 0 1994 280 1995 264 1996 365 1997 466 1998 345 1999 443 2000 447 2001 489 2002 552 2003 598 2004 644 2005 660 2014 15500 2015 15500 2017 16000 2019 16000 2020 16000 2021 16000