Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 533.617004394531 | Thousand metric tons | NA |
| 2004 | 631.401977539063 | Thousand metric tons | 18.32% |
| 2005 | 531.890991210938 | Thousand metric tons | -15.76% |
| 2006 | 512.276977539063 | Thousand metric tons | -3.69% |
| 2007 | 719.221008300781 | Thousand metric tons | 40.40% |
| 2008 | 1466.90405273438 | Thousand metric tons | 103.96% |
| 2009 | 630.393981933594 | Thousand metric tons | -57.03% |
| 2010 | 932.158996582031 | Thousand metric tons | 47.87% |
| 2011 | 1340.01293945313 | Thousand metric tons | 43.75% |
| 2012 | 931.880004882813 | Thousand metric tons | -30.46% |
| 2013 | 1243.66003417969 | Thousand metric tons | 33.46% |
