| Year | Count |
|---|---|
| 1970 | 53 |
| 1971 | 154 |
| 1972 | 362 |
| 1973 | 614 |
| 1974 | 1,165 |
| 1975 | 1,474 |
| 1976 | 2,588 |
| 1977 | 3,141 |
| 1978 | 2,816 |
| 1979 | 2,545 |
| 1980 | 3,410 |
| 1981 | 5,509 |
| 1982 | 4,018 |
| 1983 | 3,777 |
| 1984 | 6,194 |
| 1985 | 4,363 |
| 1986 | 3,352 |
| 1987 | 2,899 |
| 1988 | 2,364 |
| 1989 | 2,061 |
| 1989 | 7 |
| 1990 | 1,274 |
| 1991 | 1,250 |
| 1992 | 677 |
| 1993 | 478 |
| 1994 | 291 |
| 1995 | 195 |
| 1996 | 148 |
| 1997 | 94 |
| 1998 | 47 |
| 1999 | 32 |
| 2000 | 20 |
| 2001 | 5 |
| 2002 | 20 |
| 2003 | 16 |
| 2004 | 41 |
| 2005 | 24 |
| 2006 | 6 |
| 2007 | 28 |
| 2009 | 17 |
| 2010 | 28 |
| 2014 | 5 |