Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1518 | Thousand metric tons | NA |
| 2004 | 1738 | Thousand metric tons | 14.49% |
| 2005 | 1417 | Thousand metric tons | -18.47% |
| 2006 | 1584.59997558594 | Thousand metric tons | 11.83% |
| 2007 | 1598.64099121094 | Thousand metric tons | 0.89% |
| 2008 | 1592.66296386719 | Thousand metric tons | -0.37% |
| 2009 | 1368.34399414063 | Thousand metric tons | -14.08% |
| 2010 | 1292.00402832031 | Thousand metric tons | -5.58% |
| 2011 | 1539.44201660156 | Thousand metric tons | 19.15% |
| 2012 | 1209.48999023438 | Thousand metric tons | -21.43% |
| 2013 | 1300 | Thousand metric tons | 7.48% |
