Bituminous Coal, Number of Undercutting Machines in Use at the End of the Year for United States (A01274USA155NNBR)

Source: National Bureau of Economic Research  

Release: NBER Macrohistory Database  

Units:  Number, Not Seasonally Adjusted

Frequency:  Annual

Data Include Undercutting Machines Used In Lignite Mines. Source: Mineral Resources Of The U.S., 1923, 1927, 1929, 1930, 1931; Minerals Yearbook, 1932 And Following Issues.

This NBER data series a01274 appears on the NBER website in Chapter 1 at http://www.nber.org/databases/macrohistory/contents/chapter01.html.

NBER Indicator: a01274