As already mentioned, however, the increase in performance for Mexico is statistically significant for the period between 2003 and 2009. The percentiles for Mexico's trends in reading are presented in Figure 1.2. The comparatively weak link between performance and social background, however, should be interpreted in light of the fact that a third of 15-year-olds still need to be included into schools. Countries are sorted by the magnitude of change in reading performance from PISA 2000 to PISA 2009 (second column).