Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 660.793029785156 | Thousand metric tons | NA |
| 2004 | 667.838989257813 | Thousand metric tons | 1.07% |
| 2005 | 647.934020996094 | Thousand metric tons | -2.98% |
| 2006 | 515.539001464844 | Thousand metric tons | -20.43% |
| 2007 | 551.030029296875 | Thousand metric tons | 6.88% |
| 2008 | 605.8759765625 | Thousand metric tons | 9.95% |
| 2009 | 291.75 | Thousand metric tons | -51.85% |
| 2010 | 402.476013183594 | Thousand metric tons | 37.95% |
| 2011 | 432.471984863281 | Thousand metric tons | 7.45% |
| 2012 | 410.412994384766 | Thousand metric tons | -5.10% |
| 2013 | 492.399993896484 | Thousand metric tons | 19.98% |
