[1]The estimates of railroad cars loaded (at bottom of columns) are not exact for the time periods specified. Weekly railroad cars loaded are not prorated to a daily basis. For the current year, the estimates include railroad cars loaded for the week that includes January 1, and, therefore, can include railroad cars loaded on days in the prior calendar year, which makes the estimate slightly larger than an exact year-to-date aggregate. For the previous year, the estimates can include extra days both at the start and at the end of the year-to-date period. The week that includes January 1 can include railroad cars loaded on days that occurred in the prior year. The ending date (previous year)--as specified at the top of the year-to-date column--stops short of a full week ending on a Saturday in the previous year. But the previous year-to-date aggregation includes a full week's worth of railroad car loadings for that last week, which makes the estimate slightly larger than an exact year-to-date aggregate. By contrast, coal production is prorated to a daily basis and the year-to-date aggregates of produced tons of coal are exact for the time periods specified. 
   * For quantity data, the value of the number is less than 0.5 thousand short tons. For percent change, the value of the number is less than 0.05 percent. 
   Notes: Total may not equal sum of components because of independent rounding. Bituminous and Lignite Total includes bituminous coal, subbituminous coal, and lignite, and Anthracite Total includes Pennsylvania anthracite. The States in the Appalachian Region are Alabama, Eastern Kentucky, Maryland, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia. The Interior Region States are Arkansas, Illinois, Indiana, Iowa, Kansas, Western Kentucky, Louisiana, Mississippi, Missouri, Oklahoma, and Texas. The Western Region States are Alaska, Arizona, California, Colorado, Montana, New Mexico, North Dakota, Utah, Washington, and Wyoming. Monthly coal production estimates are usually released for printing on Friday of the first full week of the following month. 
   Sources: Association of American Railroads, Transportation Division, Weekly Statement CS-54A; for western States, special thanks to Burlington Northern Santa Fe Railway and to Union Pacific Railroad for their assistance and for trainload and carload statistics; and, Mine Safety and Health Administration, U.S. Department of Labor, Form 7000-2, "Quarterly Mine Employment and Coal Production Report."