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Last updated: 27/08/2005

Methodological bases


Timing of the evaluation (when?)


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What does this mean?

An evaluation can be performed before, during or after the evaluated intervention. Depending on the timing, its purpose and use will differ.

What is the point?

  • To optimise the resources allocated to the evaluation by launching it at the time it is likely to have the most added value.
  • To meet the needs of the main users of the evaluation at the most appropriate time.
  • To ensure that a critical mass of results and impacts are already materialised in the field and they are ready for data collection.
  • To avoid conflict with the concomitant exercises of review or audit.


Different times of an evaluation

Ex ante

An ex ante evaluation is performed before adopting or implementing the intervention. It gives support to the intervention design and contributes to ensuring the design quality. It is concerned with the following points:

  • Need to satisfy in the short or in the long run.
  • Objectives to be met.
  • Expected results and necessary indicators for their evaluation.
  • Added value of the community intervention.
  • Risks linked to the proposals.
  • Open alternative options.
  • Lessons from similar experiences already undergone.

It aims at having a direct influence on the decisions upstream from the implementation, to the extent that it transposes lessons from past experiences into the framework of the new intervention.

Mid-term or final

An evaluation during or at the end of the implementation is intended to draw lessons from the first years of the intervention implementation and to adjust the contents of the ongoing intervention in relation to realities in the field and/or contextual developments. It often includes a report on outputs and an analysis of the first results and impacts achieved. It aims at improving the intervention under way and its conclusions may be supported by observations in the field.

Ex post

The ex post evaluation is performed right after or a long time after completion of implementation. It is mainly concerned with checking achieved impacts, identifying and judging unexpected impacts and assessing the sustainability of the intervention's benefits.

It enables to detect the real changes in the field and, if the changes occur soon enough, they can be analysed to estimate those that are attributable to the intervention.

The ex post evaluation often aims to report to the institutions that have allocated the resources. Likewise, it helps to transfer acquired experiences to other countries or sectors.



  • Mid-term evaluation offers a good compromise between utility and reliability, especially if it takes place in the second half of the cycle.
  • If the evaluation is to draw on the experience of previous programmes in order to improve future ones, it is recommended to establish a multiannual evaluation plan covering several programming cycles.