Acknowledgments US Department of Transportation - BTS

Appendix EData Source and Accuracy StatementsChapter 4 Energy and the EnvironmentPETROLEUM SUPPLYTABLE 4-1. Overview of U.S. Petroleum Production, Imports, Exports, and ConsumptionThe petroleum supply system is extremely complicated, with many different processes, products, and entitiesinvolved. Briefly, crude oil is produced or imported, transported to refineries where it is refined into various products,and then transported to markets. Imports and exports of crude oil and products must be accounted for, as must benonpetroleum components of final products, such as natural gas plant liquids and ethanol for gasoline blending.The U.S. Department of Energy, Energy Information Administration (EIA) collects extensive data at select points inthe petroleum supply system. Sixteen surveys are conducted by EIA's Petroleum Supply Reporting System to trackthe supply and disposition of crude oil, petroleum products, and natural gas plant liquids:• five weekly surveys cover refineries (form EIA-800), bulk terminal stocks (form EIA-801), product pipelines(form EIA-802), crude stocks (form EIA-803), and imports (form EIA-804).• eight monthly surveys cover the same five points plus tanker and barge movement (form EIA-817), gasprocessing facilities (form EIA-816), and oxygenates (form EIA-819M).• one survey (form EIA-807) collects propane data on a monthly basis in the warmer months (April-September) and on a weekly basis in the colder months.• one annual survey determines production capacity of oxygenates and fuel ethanol (form EIA-819A), and• one annual survey determines refinery fuel use, capacity, and crude oil receipts by transportation mode(form EIA-820).The five weekly surveys target key points in the petroleum supply system. They do not include all companies, butsample 90 percent of volume at each selected point in the supply system. EIA rank-orders the companies involved inthe survey and sends surveys as it scrolls down the list, stopping when it reaches the 90 percent level. Although 100percent coverage is sacrificed, this method keeps the level of incoming data manageable and avoids burdening thesmallest companies. All data are reviewed and anomalies checked.Monthly surveys provide data that are used in the monthly and annual reports. They are similar to the weeklysurveys, but are more exhaustive in both the range of data collected and the depth of the collection. Sample sizesand response rates for several of the key points in the supply system are shown in table 1.The eight monthly surveyscover the industry more accurately than the weekly surveys and provide some double-check points that the othersurveys do not. EIA expends considerable effort to ensure that its data are as accurate as possible. Revisions aremade throughout the year. For example, EIA's Annual Energy Review 1996, released in July 1997, provided apreliminary 1996 number for total petroleum production of 8.30 million barrels per day (mmbd). The Annual EnergyReview 1997, released a year later, revised that to 8.25 mmbd, and the 1999 Review reported 8.29 mmbd.No complicated survey is likely to be 100 percent accurate. EIA lists four sources of potential systematic errors:1. Some members of the target population are missed. EIA reports that it continually reviews the lists andsearches industry periodicals and newspapers to identify new actors. Considering the nature of thepetroleum industry, it is very unlikely that companies with significant production are not surveyed.2. Some members of the target population do not respond. EIA reports a 97 percent response rate for monthlysurveys. For some points in the supply system, the average response is over 99 percent. Surveyrespondents are required by law to respond, but some nonresponse is inevitable, especially among smallcompanies. EIA assumes that the nonrespondent's value for that month is the same as for the previousmonth except for imports. Since imports vary widely, with respondents frequently having no imports, EIAassumes a nonresponse means zero imports. It can be assumed that EIA is good at "filling in the blanks."