Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 300.707000732422 | Thousand metric tons | NA |
| 2004 | 473.207000732422 | Thousand metric tons | 57.36% |
| 2005 | 461.242004394531 | Thousand metric tons | -2.53% |
| 2006 | 446.239990234375 | Thousand metric tons | -3.25% |
| 2007 | 456.665985107422 | Thousand metric tons | 2.34% |
| 2008 | 472.611999511719 | Thousand metric tons | 3.49% |
| 2009 | 364.157012939453 | Thousand metric tons | -22.95% |
| 2010 | 531.161010742188 | Thousand metric tons | 45.86% |
| 2011 | 516.77197265625 | Thousand metric tons | -2.71% |
| 2012 | 615.255981445313 | Thousand metric tons | 19.06% |
| 2013 | 500 | Thousand metric tons | -18.73% |
