http://onpoint.wbur.org/2016/04/05/panama-papers-global-corr...
The part I have transcribed below starts at 23:29.
Tom Ashbrook (NPR host): "Gerard, why weren't there more american papers, more american news organizations involved in this investigation - New York Times not part, Washington Post ... not part of it - why not, Gerard?"
Gerard Ryle (Director of the ICIJ): "We found it very difficult to get major US newspapers or organizations to collaborate. I guess they feel that they are big enough on their own, they don't need to do this, whereas we found it much easier outside the US to get people to listen to this new way of working. And that's really,... it's been driven by necessity."
Tom Ashbrook: "Was it because you weren't prepared to share all the data with these papers?"
Gerard Ryle: "No, that's not the issue at all. We were absolutely prepared to share everything from day one. What we want them to do though is join the investigation with us and with our colleagues around the world and go on a journey together. So it's not like go at the very end and give them a fully made story - we make the stories together as we go along."