Using figures seems to create rigour, objectivity, knowledge and it facilitates comparisons. Consequently, an evalution without figures is hardly conceivable. Nonetheless, objectivity and precision can be just an impression given the fact that figures are constructions built on a modeled description of reality. The simplification of reality operated through a figure can hide subtle elements regarding the way public policies work. If figures can legitimately be used in evaluation, every kinds of figures and evaluations are not equivalent. Therefore, our main research question is what place for figures in evalution? This contribution relates to research about policy evaluation, seen as a mean to produce knowledge useful for the understanding of policies and their implementation. Based on the analysis of the evaluations of rural development policies conducted by the French ministry of agriculture our goal is to increase practical and theoretical knowledge of those policies through well-designed evalutions.