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September 24, 2012

EIA improves its monthly propane imports series

Graph of Initial and Revised Reported U.S. Propane Imports from Janurary 2010 through May 2012, as explained in article text

The U.S. Energy Information Administration (EIA) recently updated its Petroleum Supply Monthly data series for propane as part of a continual effort to improve the quality of its information. As a result, EIA's May 2012 Petroleum Supply Monthly data showed a sharp apparent increase (71 thousand barrels per day) in U.S. imports of propane compared to April 2012. More accurate reporting rather than market conditions explains this increase in reported imports. The United States remains a net exporter of propane.

The sale of certain assets used for transporting propane from Canada to the United States highlighted the underreporting of historical propane imports. Reporting by the new owner of the assets was substantially different from historical reporting by the former owner, leading EIA to investigate the discrepancy. As a result, EIA revised propane import data back to the beginning of 2011.

Initial monthly reporting of propane imports for May 2012 included more accurate data. This higher level caused an apparent increase of propane imports in May (see jump in brown line between April and May).

The data correction occurred as part of EIA's ongoing process of data quality assurance and revision. EIA initially estimates petroleum supply data, including propane imports, based on weekly sample surveys. Typically, more accurate data from monthly surveys then follows these weekly estimates. Final revised monthly data for each calendar year are published during the following summer. In this case, weekly reporting from the new owners of the asset was inconsistent with previously reported data for those particular assets that were just purchased.

So, EIA initiated discussions with the new company about the data. After determining that the new higher imports were correct, EIA published the new data for the first time in monthly data for May 2012 and in final revised data for 2011. Preliminary revisions to monthly propane imports and other petroleum supply data for January-April 2012 are included in the "revised monthly reporting" line in the graph and are available in Appendix C of the Petroleum Supply Monthly.

The correction of data for 2011 does create a disconnect between the propane imports data for 2010 and 2011, with the latter year reflecting the correction in reporting while previous years do not. Going forward, however, these revisions represent a marked improvement in the accuracy of EIA's propane supply data.