Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1667.85095214844 | Thousand metric tons | NA |
| 2004 | 1371.96899414063 | Thousand metric tons | -17.74% |
| 2005 | 1845.8330078125 | Thousand metric tons | 34.54% |
| 2006 | 1917.65600585938 | Thousand metric tons | 3.89% |
| 2007 | 2357.67407226563 | Thousand metric tons | 22.95% |
| 2008 | 1681.26098632813 | Thousand metric tons | -28.69% |
| 2009 | 1477.53198242188 | Thousand metric tons | -12.12% |
| 2010 | 1532.1240234375 | Thousand metric tons | 3.69% |
| 2011 | 1888.67602539063 | Thousand metric tons | 23.27% |
| 2012 | 1843.9150390625 | Thousand metric tons | -2.37% |
| 2013 | 1500 | Thousand metric tons | -18.65% |
