The legitimacy of a pension system or any social security program depends on its credibility and perceived fairness. In order to gauge this legitimacy, we need to understand the relation between people's knowledge and attitudes. This experimental survey into the role of knowledge and perceptions divided respondents into two groups: the ‘treatment’ group received an information letter about a forthcoming pension reform before they were interviewed, while the control group was interviewed without receiving this ‘treatment’. Comparisons of the responses from the two groups allow us to assess how the level of knowledge and the provision of information affect people's opinions on policy reform. We also consider the patterns of covariation between background factors, people's concerns, and attitudes toward pension reform. The results show that the information letter had a significant impact on subjective but not on the objective level of knowledge. Receiving the information letter improved acceptance and perceptions of the fairness of the reform.