| Years | Regular Sample Discharges (in millions) | Total Sample Discharges (in millions) |
|---|---|---|
| 1988 | 5,242,904 | 5,265,756 |
| 1989 | 6,067,667 | 6,110,064 |
| 1990 | 6,156,638 | 6,268,515 |
| 1991 | 598,427 | 6,156,188 |
| 1992 | 6,008,001 | 6,195,744 |
| 1993 | 6,538,976 | |
| 1994 | 6,385,011 | |
| 1995 | 6,714,935 | |
| 1996 | 6,542,069 | |
| 1997 | 7,148,420 | |
| 1998 | 6,827,350 | |
| 1999 | 7,198,929 | |
| 2000 | 7,450,992 | |
| 2001 | 7,452,727 | |
| 2002 | 7,853,982 | |
| 2003 | 7,977,728 | |
| 2004 | 8,004,571 | |
| 2005 | 7,995,048 | |
| 2006 | 8,074,825 |