We seek feedback and advice about how we estimate the gap from external and internal subject matter experts. Based on this advice, we have assessed our estimate as reliable.
The methodology employed and the reliability assessment reflects the nature of the fuel excise system and data available to us:
- the population size is very small, and our activities confirm overall high levels of compliance
- our main data source is an external survey of large-scale petroleum and diesel producers. We have some reservations about how we employ this data including assumptions of volume sales due to temperature changes
- small producers are not covered through this survey, but their market share is negligible given the small number of participants in the fuel industry.