Heather Buchan and three co-authors, Effectiveness of strategies to encourage general practitioners to accept an offer of free access to online evidence-based information: a randomised controlled trial

From the abstract: This study examined the effectiveness of seven different interventions designed to increase the proportion of general practitioners (GPs) accepting an offer of free access to an online evidence-based resource....Australian GPs (n = 14,000) were randomly selected and assigned to seven intervention groups, with each receiving a different letter. Seven different strategies were used to encourage GPs to accept an offer of two years free access to an online evidence-based resource (BMJ Clinical Evidence)....In the group with no research demands, 27% accepted the offer. Average acceptance across all other groups was 10%. There was no advantage in using additional strategies such as financial incentives, opinion leader support, offer of professional development points, or an educational aid over a standard letter of offer to increase acceptance rates....