Population data We use the 2015 UN World Population Prospect (WPP15) as our reference for population data.1 The 2016 population estimates are based on the medium fertility variant projection. Normalising displacement data by country population size To illustrate the magnitude of internal displacement at the country level, we normalise the data to account for population size. In doing so, a clear distinction has to be made between the notion of population and inhabitants. When displacement is acute, including refugees fleeing across international borders, the population in a country at a given time may be significantly lower than the official figure. Syria is the most graphic case in point, but the issue also affects other countries such as Libya and Somalia, for which there are no up-to-date and reliable national population figures. As such, the ratios of IDPs to population and inhabitants will differ, but both provide useful information for research and analysis. Income groups and geographical region Income groups and geographical groups are based on the World Bank’s classification.2 Accounting for displacement associated with conflict and violence We produce our figures for displacement associated with conflict and violence via country-level, or situational monitoring. That is, we learn of a displacement situation and begin collecting data on it over time. the number of births and deaths in displacement. We calculate our figures as follows: New displacement We may calculate the new displacement inflow for a given year, represented by the orange “internal displacement” arrow in figure A.1, in a number of ways. If our partners provide us with data on new displacement once a year, we simply report the annually aggregated figure. More often, however, they provide us with such data on a monthly or quarterly basis, in which case we publish the sum of the estimates reported. For Ukraine, we analysed data on IDPs as recorded by the Ministry of Social Policy. These records cover the whole 2016 calendar year, providing the number of people displaced at a given date. Positive differences between two data points give some indication of the minimum number of displacements that occurred in that time interval (see figure A.2). It should be noted that “new displacement” is somewhat misleading in that data may capture the same people being displaced more than once during the year. Given that we are unable to track individual IDPs, it is often not possible to determine the extent to which this is the case for the numbers reported. The current lack of disaggregated data on IDPs who fail to achieve durable solutions, and on cross-border returns to displacement, also means that such inflows are taken as incidents of new displacement. Capturing the end of displacement We calculate annual return flow estimates in a similar way to those for new displacement. For Yemen, the aggregated return flow for 2016 represents the sum of the reported monthly figures (see figure A.3). We have historically published three main figures – the total number of people displaced as of the end of the year, the number of new displacements during the year and the number of people who returned during the year. Where possible, we have also reported on the number of IDPs who have settled elsewhere or integrated locally, those who have sought safety by continuing their flight across an international border and METHODOLOGICAL ANNEX 97