Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1529 | Thousand metric tons | NA |
| 2004 | 1471.91101074219 | Thousand metric tons | -3.73% |
| 2005 | 1582.248046875 | Thousand metric tons | 7.50% |
| 2006 | 1737.21997070313 | Thousand metric tons | 9.79% |
| 2007 | 1750 | Thousand metric tons | 0.74% |
| 2008 | 2100 | Thousand metric tons | 20.00% |
| 2009 | 2348.38989257813 | Thousand metric tons | 11.83% |
| 2010 | 2638.09594726563 | Thousand metric tons | 12.34% |
| 2011 | 3228.93090820313 | Thousand metric tons | 22.40% |
| 2012 | 3749.86010742188 | Thousand metric tons | 16.13% |
| 2013 | 3750 | Thousand metric tons | 0.00% |
