The CERP approach is a dynamic one. For each nation in each year, indicators of responsibility and capacity, together with a variety of macro-economic data that together define national development need (estimated by way of a development threshold) are used to calculate a Responsibility and Capacity Index, or RCI. The exact definitions of responsibility, capacity, and development need, and the relative weighting given to responsibility and capacity, are chosen by the user.
The national RCI is then used to determine the national fair share of the global mitigation requirement, which is also based on a global “no policy baseline” and on the user’s choice of a global mitigation pathway. The following figure illustrates the method here, by showing a global mitigation requirement that is partitioned into national fair shares, which are assigned to individual countries on the basis of their dynamically shifting responsibility and capacity.