Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2028 | Thousand metric tons | NA |
| 2003 | 1953 | Thousand metric tons | -3.70% |
| 2004 | 2150 | Thousand metric tons | 10.09% |
| 2005 | 2120 | Thousand metric tons | -1.40% |
| 2006 | 2115 | Thousand metric tons | -0.24% |
| 2007 | 2100 | Thousand metric tons | -0.71% |
| 2008 | 2494 | Thousand metric tons | 18.76% |
| 2009 | 1575 | Thousand metric tons | -36.85% |
| 2010 | 1553 | Thousand metric tons | -1.40% |
| 2011 | 1811 | Thousand metric tons | 16.61% |
| 2012 | 1798 | Thousand metric tons | -0.72% |
