IDPs unfortunately don't fall under UNHCR's mandate formally, although of course the UNHCR has been responding in a number of IDP contexts across the world and over the years. They are right now in a process of developing their IDP policy, which seeks to clarify what UNHCR's engagement in an IDP context is going to be, both in terms of operational coordination and also in data collection and protection more broadly.
We are encouraging them to bring as much clarity as possible so that their response in the future can be as predictable and as comprehensive as possible, but we do have some concerns that along with what looks to be an ambitious IDP policy, the budget for responding in an IDP context is decreasing and is still significantly lower than their budgets for responding to refugee flows.
The problem with internal displacement is that there is a clear gap in terms of international leadership and governance on this issue, because no single UN agency is formally responsible for the internal displacement agenda. That counts for UNHCR, just as it does for IOM, OHCHR, UNDP, and so on.