Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 27314 | Thousand metric tons | NA |
| 2004 | 27556 | Thousand metric tons | 0.89% |
| 2005 | 27309 | Thousand metric tons | -0.90% |
| 2006 | 27559.40625 | Thousand metric tons | 0.92% |
| 2007 | 29436.783203125 | Thousand metric tons | 6.81% |
| 2008 | 31042.78125 | Thousand metric tons | 5.46% |
| 2009 | 27475 | Thousand metric tons | -11.49% |
| 2010 | 31228.208984375 | Thousand metric tons | 13.66% |
| 2011 | 42212.71875 | Thousand metric tons | 35.17% |
| 2012 | 40000 | Thousand metric tons | -5.24% |
