Measurable and attributable
Project participants are required to calculate leakage, which is defined as:
...the net change of anthropogenic emissions by sources of greenhouse gases which occurs outside the project boundary, and which is measurable and attributable to the CDM project activity (3/CMP.1, Annex, paragraph 51).
In this context, 'measurable and attributable' means:
..."which can be measured" and "directly attributable", respectively (CDM Glossary of Terms, Version 03).