Farm-based agricultural shipments represent one of the most significant OOS areas for the CFS.  This sector covers farm-based agricultural shipments from the field (i.e., farm) to grain elevator, distribution or processing center, or slaughterhouse.  These shipments are almost entirely moved by truck, therefore under FAF4, it is assumed that truck is the mode of transportation used for transporting all farm-based agricultural shipments.

5.1 DATA SOURCES

5.1.1 2012 Census of Agriculture

The Census of Agriculture is a census conducted every five years by the U.S. Department of Agriculture (USDA); it coincides with the Economic of Census, which occurs in years ending “2” and “7.”  The Census of Agriculture is the leading source of facts and statistics about U.S. agricultural production.  It provides statistical information at the national, state, and county (or county equivalent) levels.  All agricultural production establishments (e.g., farms, ranches, nurseries, greenhouses, etc.) are included² in the census.  The latest available data from the Agriculture Census is for 2012.

5.1.2 Agricultural Statistics 2013

The Agricultural Statistics is an annual publication prepared by the National Agricultural Statistics Service (NASS) of the USDA.  It provides information on agricultural production, supplies, consumption, facilities, costs, and returns.  Weights, measures, and conversion factors are also published in this reference book.  Information from the 2013-issue of this publication was used for FAF4, and includes preliminary estimates for 2012 and projection estimates for 2013.

5.1.3 USDA Statistical Bulletins

The NASS of the USDA issues a series of bulletins that contain final estimates for agricultural data series based on the review of the 2012 Census of Agriculture and other information.  A large number of bulletins covering all major types of agricultural commodities have been published by the NASS in this series. 

5.1.4 2002 Vehicle Inventory and Use Survey (VIUS)

As a part of the Economic Census, the Bureau of Census collects information on the physical and operational characteristics of the private and commercial truck population in the U.S.  The VIUS had been conducted in the same year as the CFS (also a part of the Economic Census).  However, this program was terminated prior to the 2007 Economic Census, making the 2002 VIUS the latest available data in this series. 

Note that in FAF3, 2002 VIUS data was used to estimate the average travel distance for farm-based agricultural shipments covered under this data gap.  Although continued use of this decade old data set for FAF4 purposes was a concern, lack of recent and complete data makes the 2002 VIUS the best source.  That is, without updated information, it is assumed that distributions of farm-based shipment distances (in terms of distance from field to the first-point processing center such as grain elevator, distribution or processing center, or slaughterhouse, etc.) remained the same over the last decade.

5.1.5 2012 CFS Published Statistics

Tonnage and value by origin information from the 2012 CFS for shipments of SCTG 01, 02, 03, 04, 05, 07, and 09 were used to determine associated farm-based shipment origin-destination flows.  More details on the use of CFS 2012 data are discussed in the estimation methods section below.

5.2 ESTIMATION PROCEDURES

5.2.1 Estimating Agricultural Production at State Level

The dollar value of this OOS data gap at the national and state levels can be estimated using information obtained from the 2012 Census of Agriculture and related publications.  Specifically, data provided under the category of “Market value of agricultural products sold”³ was used as an estimate for total farm-based agricultural shipments.  The estimation of tonnages for these OOS shipments is not as straightforward, however.

The USDA’s commodity tonnage statistics in the 2012 Census of Agriculture are typically in different units of measurement (e.g., pounds, bushels, hundredweight, barrels, tons, etc.).  Therefore, unit conversions were necessary.  In many cases, the conversion factors⁴ are different even though the “same” unit was used.  For example, the approximate net weight for a bushel of wheat is 60 pounds, while a bushel of corn is 70 pounds for husked corn on the cob, and 56 pounds for shelled corn.  All conversion factors used in this study are based on information obtained from Agriculture Statistics 2013.

Because the USDA does not use SCTG codes for its commodity categorization, agricultural commodities were regrouped into SCTG categories, to the extent possible and reasonable.  A more detailed regrouping of SCTG commodities (than that used in FAF3) is established for FAF4.  As a result, accuracy of estimates for this OOS area has improved.  Note that categories of farm-based agricultural shipments considered in FAF4 are more comprehensive than that under FAF3 where only SCTG 01, 02, and 03 were included. 

Results from the 2012 Census of Agriculture data indicated that this farm-based OOS component involved nearly 1 billion tons valued at $385 billion in 2012. Table 5–1 shows the breakdown of this total by SCTG at the national level.  Itemized farm-based agricultural products included in these national totals are provided in Appendix B.  

Table 5–1 .  National Total for Farm-Based Agricultural Shipments in 2012

5.2.2 Estimating Agricultural Production at FAF-Zone Level (Origin of Shipments)

In addition to state-level statistics, a similar level of details in commodity weights can also be obtained at the county level for many agricultural commodities using data provided by USDA.  Thus, the method used in estimating state-level tonnage statistics can be applied to generate estimates at the county level for those commodities. 

For commodities that tonnage statistics cannot be directly estimated from USDA-published data, harvested acreages for those commodities are provided at the county level (instead of their weights).  Although acreage does not necessarily mean production, it is clear that no production of a given agricultural commodity is possible if no acreage was designated for that.  Under this study, when the weight information of a commodity was not given, a straightforward method of using the acreage data to proportional distribute the state-level total weight of the given agricultural product to counties involved (within the given state) was utilized.  This proportional distribution method was used to disaggregate state-level total shipment value into county-level values as well.  Clearly, this process is only necessary for states with sub-state FAF zones (i.e., CFS areas).  County-level production estimates (tonnage and value) within each CFS area were summed to obtain the given zonal-level estimates. 

5.2.3 Estimating Farm-Based Shipment OD Flows

Determining Destinations of Farm-Based Shipments 

In order to estimate OD flows of farm-based agricultural shipments, destinations of those shipments had to be determined first.  The criteria used in selecting potential destinations of farm-based shipments are different from FAF3.  Under the FAF3 process, only CFS areas that shipped out the same commodity (i.e., SCTG) were used to determine the terminating geography of the given SCTG shipments from a farm.  The FAF4 process expanded this destination selection process to consider CFS areas that shipped out products associated with the farm-based commodity.  For example, CFS areas with shipments of “tobacco products” (SCTG 09) that originated from their locations were considered as potential destinations for “tobacco harvested” (SCTG 03) from a farm. 

Estimating OD Flows of Farm-Based Shipments

As in FAF3, VIUS 2002 data was used in estimating the distribution of average shipment distances.  Specifically, VIUS data provides information on the typical “area of operation” of trucks carrying agricultural products.  This information is given in categories such as: off-the-road; 50 miles or less; 51 to 100 miles; 101 to 200 miles; 201 to 500 miles; 501 miles or more; not reported; and not applicable (i.e., vehicle not in use).  Because the primary interest of FAF is on commodity movements on the national transportation systems, off-road activities were not applicable to this study.  Furthermore, since farm-based shipments were generally assumed to be relatively local (shorter trips), the category of “501 miles or more” was also eliminated from the estimation process.  Using mid-points of the remaining range categories and the distribution of operating ranges, a distribution of shipment length can be estimated for each of the associated SCTG commodity-carrying truck groups (i.e., principal product carried) by state.  A brief discussion of a similar estimation procedure, at the state level, can be found in a 1998 Journal of Transportation and Statistics article.⁵

When multiple destinations (CFS-based) are within the same distance range from a given “production” area (i.e., origin of the farm-based shipment), the estimated total of this shipment is divided proportionally among all involved destination regions, based on the tonnages of each associated commodity.  The same method is applied to the estimation of dollar values on farm-based shipments.

As an illustration of this process, assume there are agricultural product (SCTG 03) shipments originating from the “Rest of IN” (FAF4 zone 189), which weights 100 thousand tons in total.  (For simplicity of this example, it is assumed no tobacco-related products are involved.)  Based on the 2002 VIUS data, 94% of Indiana-based trucks that moved agricultural shipments traveled within 50 miles.  Thus, in this example, 94 thousand tons of these shipments will be moved within a 50-mile radius of the origin zone ‘189’. 

With the aid of a Geographic Information System (GIS) tool, four CFS areas are identified as within the 50-mile range (measured from centroid to centroid of two zones) of zone ‘189.’  These four zones along with their associated CFS tonnages (amount originating from each given zone) for the selected commodity are listed in Table 5–2. 

Table 5–2 .  Total Tonnages Originated from CFS Areas within a 50-mile Distance Range of FAF4 Zone 189 for SCTG03

Using the shares obtained from Table 5–2, the 94 thousand tons of SCTG 03 originating from zone ‘189’ are proportionally distributed to four destinations zones: 211, 183, 182, and 189.  As a result, four OD flows are created for this example case, all with commodity SCTG 03 and domestic mode of truck.  Table 5–3 presents the assigned OD pairs and their shipment tonnages for the example case.

Table 5–3 . Resulting OD Flows for the SCTG03 Shipment Example

² The definition of a farm in the Census of Agriculture is “any place from which $1,000 or more of agricultural products were produced or sold, or normally would have been sold, during the census year.”  This definition is consistent with the definition used for current USDA surveys.

³ The “Market value of agricultural products sold” category represents the value of products sold which combines total sales not under production contract and total sales under production contract.  It is equivalent to total sales.  See Appendix A, General Explanation and Census of Agriculture Report Form, in the 2012 Census of Agriculture report for further explanation.

⁴   “Weights, Measures, and Conversion Factors” table in the Agricultural Statistics 2013 publication at:  http://www.nass.usda.gov/Publications/Ag_Statistics/2013/Agricultural_Statistics_2013.pdf.

⁵ Chin, S. M., J. Hopson, and H. L. Hwang, “Estimating State-Level Truck Activities in America,” Journal of Transportation And Statistics, Volume I, No. 1, pp 63-74, January 1998.