Does the geographic proximity effect on knowledge spillovers vary across research fields?

Policy makers are interested in the influence of geographic distance on knowledge flows, however these can be expected to vary across research fields. The effects of geographic distance on flows are analyzed by means of citations to scientific literature. The field of observation consists of the 2010-2012 Italian publications and relevant citations up to the close of 2017. The geographic proximity effect is analyzed at national, continental, and intercontinental level in 244 fields, and results as evident at national level and in some cases at continental level, but not at intercontinental level. For flows between Italian municipalities, citations decrease with distance in all fields. At continental level, four fields are identified having knowledge flows that grow with distance; at intercontinental level, this occurs in 26 fields. The influence of distance is more limited in the fields of Humanities and Social sciences, much more significant in the Sciences, mainly in the Natural sciences.