As part of the broader impact agenda at universities in the knowledge economics (and the UK, Australia and Netherlands in particular) there is growing interest in linking academic research outputs to the policy documents – government guidelines, policy briefs, white papers, impact assessments and so on – that cite them. Using Overton, a novel grey literature database of 5.5M+ full text policy documents from governments and think tanks around the world, we find while in scholarly literature the sciences tend to be highly cited, and the social sciences less so, the opposite is true in the policy literature. We find biases within policy documents from specific countries towards academic work originating in that country, and determine the citation half life and the average age of first citation in policy for a variety of different article types. We discuss how accessing and organizing the policy grey literature could help universities, funders and governments better understand the impact their outputs are having on the wider world.