the approach to weighting impacts in different regions (equity weighting).
Most impacts in the medium term occur in developing countries, and so the
decision on whether to use compensation values or adjust estimates using
a form of distributional weighting (equity weighting) has a significantly
bearing on the results. Use of equity weights increases the SCC values,
but there have been concerns raised over their use when compared to other
international policy (e.g. in the UK, see Pearce 2003; and also recent work
by Anthoff et al. 2006a). With a PRTP of 0%, and equity weighting, the
FUND model analysis showed an increase in the SCC by a factor of 5 to
15, depending on the way equity weights are calculated (see Figure 4 for
an example from a central FUND run). Even with higher discount rates,
the increase might be a factor of 2 to 10.