Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 6740 | Thousand metric tons | NA |
| 2003 | 6986 | Thousand metric tons | 3.65% |
| 2004 | 9221.4580078125 | Thousand metric tons | 32.00% |
| 2005 | 6251.96923828125 | Thousand metric tons | -32.20% |
| 2006 | 6075.89306640625 | Thousand metric tons | -2.82% |
| 2007 | 6080 | Thousand metric tons | 0.07% |
| 2008 | 5135.15087890625 | Thousand metric tons | -15.54% |
| 2009 | 5756.93603515625 | Thousand metric tons | 12.11% |
| 2010 | 3559.5791015625 | Thousand metric tons | -38.17% |
| 2011 | 3560 | Thousand metric tons | 0.01% |
| 2012 | 4692.509765625 | Thousand metric tons | 31.81% |
| 2013 | 5090.86279296875 | Thousand metric tons | 8.49% |
