Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 28600 | Thousand metric tons | NA |
| 2003 | 30460 | Thousand metric tons | 6.50% |
| 2004 | 32198 | Thousand metric tons | 5.71% |
| 2005 | 32650 | Thousand metric tons | 1.40% |
| 2006 | 35300 | Thousand metric tons | 8.12% |
| 2007 | 40000 | Thousand metric tons | 13.31% |
| 2008 | 44400 | Thousand metric tons | 11.00% |
| 2009 | 50000 | Thousand metric tons | 12.61% |
| 2010 | 61000 | Thousand metric tons | 22.00% |
| 2011 | 66000 | Thousand metric tons | 8.20% |
| 2012 | 70000 | Thousand metric tons | 6.06% |
