Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2171 | Thousand metric tons | NA |
| 2003 | 2472 | Thousand metric tons | 13.86% |
| 2004 | 2731.19995117188 | Thousand metric tons | 10.49% |
| 2005 | 3130.89990234375 | Thousand metric tons | 14.63% |
| 2006 | 3495 | Thousand metric tons | 11.63% |
| 2007 | 3820 | Thousand metric tons | 9.30% |
| 2008 | 4219 | Thousand metric tons | 10.45% |
| 2009 | 4350 | Thousand metric tons | 3.10% |
| 2010 | 4531 | Thousand metric tons | 4.16% |
| 2011 | 4604 | Thousand metric tons | 1.61% |
| 2012 | 4906 | Thousand metric tons | 6.56% |
