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  EUROPA > European Commission > EuropeAid > Evaluation > Methods > How
Last updated: 14/12/2005

Methodological bases
Evaluation process (How?)
Data collection


Using available data


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Data collection
• Overview
• Existing data
• Frequent

• Reliability

What are they?

Existing information, such as administrative data, research, previous evaluations, management and monitoring databases, statistics.

Why is it important?

  • Existing (secondary) data are cheaper and quicker to gather than primary data.
  • If the evaluation team does not acknowledge relevant existing data, this will undermine the credibility of the whole evaluation.

Main channels for identifying and gathering secondary data
  • Managers, implementing agencies, operators and partners
  • Experts in the domain under consideration
  • The Internet
  • Statistical offices and monitoring bodies
  • Scientific and professional literature


Reliability problems

Before making use of secondary data, particular attention should be paid to the following points:

  • Definitions: do the data measure/reflect what is to be addressed?
  • Missing data
  • Accuracy: are the sources and measurement method reliable?
  • Age: when did measurement actually take place?
  • Reliability over time: did definitions or measurement methods change in the period covered?
  • Comparability: are definitions and measurement methods consistent from one place to another?
  • Aggregating data: are pooled data consistent with one another?
  • Disaggregating: is it possible to break down data into sub-territories or sub-sectors while keeping a large enough statistical basis?


  • Where possible, multiple sources of evidence should be used so as to follow cross-checking.
  • Be aware of vested interests when using secondary data. Those responsible for their compilation may have reasons for showing an optimistic or pessimistic picture. For instance, it has been reported that officials responsible for estimating food shortages exaggerated the figures before sending aid requests to potential donors.