| Vuosi Year |
Määrä (1000 tonnia) Absolute amounts (1000 tonnes) |
Suhde tuotantomäärään (%) Proportional to the volume of production (%) |
| 1988 | 53.1 | 0.33 |
| 1991 | 28.1 | 0.18 |
| 1992 | 21.0 | 0.14 |
| 1993 | 15.8 | 0.09 |
| 1994 | 16.7 | 0.11 |
| 1995 | 16.9 | 0.10 |
| 1996 | 17.1 | 0.09 |
| 1997 | 17.4 | 0.07 |
| 1998 | 17.7 | 0.07 |
| 1999 | 16.9 | 0.07 |
| 2000 | 14.2 | 0.06 |
| 2001 | 14.5 | 0.06 |
| 2002 | 14.6 | 0.06 |
| 2003 | 15.0 | 0.06 |
| 2004 | 15.2 | 0.06 |
| 2005 | 15.4 | 0.06 |
| 2006 | 14.8 | 0.05 |
| 2007 | 15.7 | 0.05 |
| 2008 | 11.4 | 0.04 |
| 2009 | 10.9 | 0.04 |
| 2010 | 10.8 | 0.04 |
| 2011 | 10.6 | 0.04 |