Production estimates of the non-responding operations were based on employment data provided by MSHA. The estimated production of 4,647 non-responding operations was 750 million short tons, or 35 percent of U.S. construction aggregates production.

Unit values are determined by the average annual f.o.b. plant prices, usually at the first point of sale or captive use, as reported by the construction aggregates producing companies. This value does not include transportation from the plant or yard to the consumer. It does, however, include all costs of mining, processing, in-plant transportation, overhead costs, and profit. For those operations that reported production only, the unit values of total production or specific end uses were estimated based on other reporting operations within the same state. AM

Jason Christopher Willett is a crushed stone commodity specialist with the U.S. Geological Survey. Wallace P. Bolen is a sand and gravel commodity specialist with the U.S. Geological Survey.