Number one project management skill - providing transparency

Recently I was asked to tell about THE critical success factor for project managers from my point of view. Based on my experience I would say number one is to provide transparency to the involved stakeholders and consequently addressing different level of information needs in informal and formal formats.  
Very often people are only "confronted" with results of a meeting or workshop and they were not part of the dialogues and decisions taken during those meetings and workshops. Consequently, they are missing a kind of  "common history". And this is so important: understanding the way how decisions were taken and the according outcomes afterwards and to go through the process of a commonly built experience. 
When now talking about transparency for me it includes the process that helped to get to that particular outcome. This kind of information enlarges the thinking about problem solving in a constructive way - also for further project stakeholders who were not attending specific meetings or workshops. And it fosters change.