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Annex 4 233
Transfers category reporting
Figure 22: World natural gas shipping sales, export-import discrepancy
and statistical difference
The IEA “Transfers” category “… comprises … products transferred and recycled products. Products transferred
are intended for oil products imported for further processing in refineries. Recycled products are finished
products, which pass a second time through the marketing network …”.
Given this definition, the net balance of inter-product transfers cannot be checked if equal to zero; however,
the net balance of “Transfers” may be an indicator of a potential maximum discrepancy in the net balance of
inter-product transfers figure.
We find that the world transfers balance also is greater than zero, meaning that net transfer statistics do not
balance at the world scale – in other words, that additional fuel exists in the transfers data. If these transfers
include significant volumes of fuel or other products that were later blended for marine bunkers, the statistical
data could under-report marine bunkers consumption.
Our assessment indicates that the additional uncertainty contributed by such an allocation error would increase
the export-import adjustment by approximately 10% to approximately 20% since 1998. Figure 23 illustrates
the comparative impact on uncertainty of the observed export-import discrepancy and the observed transfers
balance discrepancy.
Data accuracy
The accuracy of the data depends on different statistical approach on data collection, reporting and validation.
For example, Marland (2008) reports that:
“… the United States national calculation of CO 2 emissions has an uncertainty (at the 95% confidence
level) of -1% to 6%, and Environment Canada reported a comparable value of -4% to 0%. Olivier
and Peters (2002) estimated that emissions from Organisation for Economic Co-operation and
Development (OECD) countries might have – on average – an uncertainty of 5% to 10%, whereas the
uncertainty may be 10% to 20% for other countries. The International Energy Agency did not report
the uncertainty of its emissions estimates but relied on Intergovernmental Panel on Climate Change
(IPCC) methodologies and cited the IPCC estimate that ‘for countries with good energy collection
systems, this [IPCC Tier I method] will result in an uncertainty range of ±5%. The uncertainty range
in countries with “less well-developed energy data systems” may be on the order of ±10%.’”