Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1171726 | Metric tons | NA |
| 2003 | 1005831 | Metric tons | -14.16% |
| 2004 | 840318 | Metric tons | -16.46% |
| 2005 | 1064200 | Metric tons | 26.64% |
| 2006 | 818000 | Metric tons | -23.13% |
| 2007 | 796900 | Metric tons | -2.58% |
| 2008 | 632600 | Metric tons | -20.62% |
| 2009 | 998530 | Metric tons | 57.85% |
| 2010 | 878376 | Metric tons | -12.03% |
| 2011 | 541200 | Metric tons | -38.39% |
| 2012 | 398500 | Metric tons | -26.37% |
