WTO members have agreed to seek a “permanent solution” to the problems that some developing countries say they face in addressing food security objectives under the trade body’s existing farm subsidy rules. Negotiators now need to construct an equitable and sustainable solution that takes into account food security objectives, based on concrete evidence about the operation of public stockholding programmes and the extent to which they might affect the functioning of global markets. This paper seeks to contribute to this process by surveying the extent to which this evidence is available, analysing the data which does exist, and drawing some initial conclusions about options that negotiators might fruitfully be able to explore.