There are two important things to consider regarding this question. Firstly, what is the available evidence on key results? Presumably this will differ from country to country.  Also, results might not be country specific but rather results related to a donor partner's set of objectives (in which case there should be no impact on national policy and priorities).  Secondly, how do we 'measure' the extent to which national policies are affected by available evidence on key results? One way might be to interview key informants who could tell us.  Another might be to scan the literature for any research that has been done in this area. Finally, one can take a bird's eye view approach and demonstrate a connection between results and policies and priorities.