In an extreme case, all of the income differences between strata in those dimensions (or changes in quintile composition according to those dimensions) could be due to the different education structures in those strata. But there is evidence suggesting that the variables reflecting different characteristics of the production structure (such as the two mentioned earlier) help explain the differences in income among employed persons, regardless of education level. These negative perceptions could stand in the way of a social covenant based on equality and should be taken account of in any strategy' aimed at expanding guarantees and core rights for the population.