This example shows that when applying own emission factors, through periodic refinement of the methodology to develop the PCDD/PCDF inventory, revisions of the previous inventories are equally needed. Besides changes in the Toolkit methodology through its revision in 2013, better information becoming available at the country level, including through direct measurements of emissions and development of more specific emission factors, is an equally important triggering factor to revise baseline estimates of releases. If the revision of the baseline is not performed, the results obtained for the different reference years are not readily comparable and trends over time cannot be estimated.