Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 16325 | Metric tons | NA |
| 2003 | 24606 | Metric tons | 50.73% |
| 2004 | 28696 | Metric tons | 16.62% |
| 2005 | 26185 | Metric tons | -8.75% |
| 2006 | 28497 | Metric tons | 8.83% |
| 2007 | 34755 | Metric tons | 21.96% |
| 2009 | 37359 | Metric tons | 7.49% |
| 2010 | 40109 | Metric tons | 7.36% |
| 2011 | 37534 | Metric tons | -6.42% |
| 2012 | 20698 | Metric tons | -44.86% |
| 2013 | 38000 | Metric tons | 83.59% |
