This paper analyses the instability of farm income experienced by a constant sample of Italian farms over the period 2003-2012. It assesses the extent of the aggregation bias due to the use of aggregated vs. single farm data and estimates the level of farm income variability in several groups of farms for the whole period and for two sub-periods. Differences between groups and periods are assessed by means of non-parametric tests. Results suggest that analyses based on aggregated farm data are likely going to strongly underestimate the extent of income variability faced by farmers. Income variability levels differ among farm groups and have significantly increased over the considered time. This has policy implications regarding the risk management tools recently introduced within the Rural Development Policies and how these should be targeted on the farms that more need them.