Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1543 | Thousand metric tons | NA |
| 2004 | 1833 | Thousand metric tons | 18.79% |
| 2005 | 1839 | Thousand metric tons | 0.33% |
| 2006 | 1900 | Thousand metric tons | 3.32% |
| 2007 | 2000 | Thousand metric tons | 5.26% |
| 2008 | 2000 | Thousand metric tons | 0.00% |
| 2009 | 1695.09997558594 | Thousand metric tons | -15.25% |
| 2010 | 2411.60009765625 | Thousand metric tons | 42.27% |
| 2011 | 2576.30004882813 | Thousand metric tons | 6.83% |
| 2012 | 2176.60009765625 | Thousand metric tons | -15.51% |
| 2013 | 2652.30004882813 | Thousand metric tons | 21.86% |
