The results for Costa Rica indicate that the ambiguous distribution shifts discussed earlier mask mixed patterns of wage performance. The bulk of median wage gains have been markedly concentrated so that instances of real wage deterioration are more common. The hardest hit were older workers with secondary education in all sectors, middle age self-employed with primary or less and the young with some or complete secondary in informal jobs. Like in Argentina, median real wage gains of formal salaried workers with higher education were notable for the young and minor for the middle age. Moreover, the strong wage growth of older informal workers with primary or less contrasts with the wage stagnation of the like formal salaried.<sup>27</sup> Overall, the picture revealed by this simple wage cell analysis fails to conform with the common presumption that economic reforms have resulted in wide regional trends of steadily rising real wages for highly educated workers in formal salaried jobs, and sluggish or even declining wages for the less educated, especially those in the informal sector. The evidence from Argentina, Brazil and Costa Rica suggests that more intricate patterns of wage growth are at play, which often position disadvantaged workers at the front line of wage gains. Among Workers with higher education, only the old formal and self-employed did consistently better across all countries. These are likely to be managers or workers with long tenures and specific human capital such as organizational knowledge that remains valuable in restructuring economies.

It is interesting to note that often both the magnitudes and patterns of wage growth are significantly modified when wage outcomes are assessed based on average (Table 4B) rather than median wages. This is particularly the case in Costa Rica and Argentina. Rather than being driven by outliers<sup>2 8</sup> or small cell samples, this points to considerable heterogeneity in wage growth within many age-education groups and sectors. As indicated by the shifts in the group-specific wage distributions, real wage changes were often far from homogeneous. More generally, differences in the distribution of unobservable factors such as individual spunk or school quality are also likely to affect differently the wage performance of observationally equivalent workers so that single measures like the mean or the median would be inappropriate to fully characterize wage performance.

In a spirit similar to the above wage density comparisons, we would also like to explore whether existing wage differentials within "counterfactual" narrowly defined groups have changed any differently over the time period. Obviously, we face severe data limitations to control for even some of the possible interrelations by partitioning workers into many different groups for which wage densities (or even average wages) can be estimated. Quantile regressions provide us with a powerful tool to come close to such characterization by revealing the relative wage perfornance of more narrowly defined "archetypical" workers. The results of this multivariate quantile analysis below indeed pinpoint important differences in the wage growth experiences of workers at different points of the conditional wage distribution.

> 27 Results for the more educated workers in informal jobs suggest notorious wage deterioration but are unreliable due to their small number.

> 28 Means are computed after trimming 3% of the observations in the tails within each group.

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