Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 20300 | Thousand metric tons | NA |
| 2003 | 21500 | Thousand metric tons | 5.91% |
| 2004 | 22300 | Thousand metric tons | 3.72% |
| 2005 | 23300 | Thousand metric tons | 4.48% |
| 2006 | 23300 | Thousand metric tons | 0.00% |
| 2007 | 24700 | Thousand metric tons | 6.01% |
| 2008 | 27713 | Thousand metric tons | 12.20% |
| 2009 | 20389 | Thousand metric tons | -26.43% |
| 2010 | 27917 | Thousand metric tons | 36.92% |
| 2011 | 22968 | Thousand metric tons | -17.73% |
| 2012 | 23000 | Thousand metric tons | 0.14% |
