It is therefore a useful complement for the earlier analysis of household income data which necessarily mixes the effects of policy and “other” changes. The advantage of the simulation is that it can hold “everything else” constant (unemployment levels, market-income inequality, household composition, etc.), For instance, it can show whether families at the bottom, middle and top of the income distribution are now better or worse off than they would have been with unchanged policies. This way of comparing the net effect of redistribution systems between different periods permits pin-pointing “gainers” and “losers” of policy reforms. The approach is an extension of OECD (2008b).