Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1902 | Thousand metric tons | NA |
| 2004 | 2108 | Thousand metric tons | 10.83% |
| 2005 | 2408 | Thousand metric tons | 14.23% |
| 2006 | 2225 | Thousand metric tons | -7.60% |
| 2007 | 2607 | Thousand metric tons | 17.17% |
| 2008 | 2600 | Thousand metric tons | -0.27% |
| 2009 | 2487.60009765625 | Thousand metric tons | -4.32% |
| 2010 | 2592.80004882813 | Thousand metric tons | 4.23% |
| 2011 | 3336 | Thousand metric tons | 28.66% |
| 2012 | 2950 | Thousand metric tons | -11.57% |
| 2013 | 2970 | Thousand metric tons | 0.68% |
