On its own, leaving a quartile doesn&#x27;t say anything about the magnitude of the change, so it&#x27;s not a very useful measure of anything.<p>Another problem is that because the distribution is so heavily skewed toward the top (for both income and wealth, but more heavily for wealth), dividing the population into equal groups creates a somewhat misleading picture of mobility. A nonlinear breakdown of classes is more reflective of the distribution. In that case we might ask something like how many people move from the bottom 40% to the top 5%.