6. Knowledge and Skills

The OECD Programme for International Student Assessment (PISA) tests the abilities of 15-year-old students in mathematics, reading and science. Scores are measured on a scale that is standardised to 500 for the OECD average. This standardisation is established in the first year a subject is introduced as the major testing domain (e.g. 2003 for mathematics), to enable comparisons over time. For this reason, the OECD average may not exactly equal 500 in any given year. Also, the reference year used for assessing changes over time varies by subject.

Japanese students have the highest average mathematics scores in the OECD, followed by Korea, Estonia and the Netherlands (Figure 6.2). At the other end of the scale, Colombia has the lowest average score, with Mexico and Chile just above. Since 2003, the average maths score of students aged 15 has significantly improved in just 8 OECD countries, but worsened in 13. The largest gains occurred in Israel (over 6 points), while Finland experienced the largest falls (almost 10 points).

In Estonia, Canada, Finland and Ireland, 15-year-old students have the highest average PISA reading scores among OECD countries, followed very closely by Korea and Poland (Figure 6.3). As in the case of maths, Colombia, Mexico and Chile have the lowest average scores. Since 2000, students’ average reading scores fell significantly in 8 OECD countries, but increased in 7. The largest increases occurred in countries falling below the OECD average (Chile, Colombia, Israel and the Russian Federation), as well as Estonia and Germany, whose performance is above average. Significant declines in reading performance primarily occurred in countries already faring relatively well (e.g. Finland, Australia and the Netherlands).

For science, average PISA scores are highest in Estonia, Japan, Finland, Korea and Canada, and lowest in Colombia, Mexico and Chile (Figure 6.4). Since 2006, science scores have increased in only three OECD countries (Colombia, Portugal and Turkey), while they have fallen in around half, a pattern that mirrors (with greater intensity) the one already observed for maths and reading.

Overall, only two OECD countries – Colombia and Portugal – have improved their scores in all three subjects over the past decade or so. An additional four (Estonia, Israel, Poland and the Russian Federation) have improved their scores in both reading and maths. Seven countries have seen their scores deteriorate in all three subjects: Australia, Finland, Iceland, Korea, the Netherlands, New Zealand and the Slovak Republic.

On average, across OECD countries, the top-performing students (those who score in the 90th percentile) have PISA scores more than 60% higher than the lowest-performing ones (those in the 10th percentile) (Figure 6.5). Inequalities are typically larger in OECD countries with comparatively poor average performance in all subject areas. Looking across reading, maths and science tests combined, Israel has the highest inequalities between high and low achievers in the OECD (followed by Luxembourg and the Slovak Republic), while several countries with strong performances on average skills (e.g. Estonia, Ireland, Denmark, Finland Japan, Poland and Canada) all have below average inequalities. Korea is an exception, with strong average performance, but also larger inequalities than in other countries performing at that level (Figure 6.6). In Colombia and Mexico, over 30% of students have low scores in all fields, while only 4.2% of students in Estonia do.

The OECD Programme for the International Assessment of Adult Competencies (PIAAC) assesses the cognitive skills of adults in numeracy, literacy and problem-solving. Unlike PISA, PIAAC results are not standardised to a fixed OECD average level, but measured on a scale from 0 to 500.

The first (and latest available) wave of the OECD Adult Skills Survey was fielded in around 2012. Numeracy scores among adults were highest in Japan, followed by Finland, Belgium (Flanders) and the Netherlands. Chile, Mexico and Turkey have the lowest scores among OECD countries. Cross-country differences in literacy scores across OECD countries generally mirror those in numeracy (Figure 6.7).

As in the case of students’ cognitive skills, OECD countries with high average numeracy scores among adults also have a more equal distribution of scores, i.e. the gap between the top (90th percentile) and bottom (10th percentile) performers is smaller. Japan, for example, has both the highest mean numeracy score among adults and the lowest gap between high and low performers. Conversely, countries with low mean scores – such as Chile and Turkey – have high levels of inequality.

The gap between the top (90th percentile) and bottom (10th percentile) performers is smaller in literacy than it is for numeracy, but the general cross-country pattern holds, and countries with lower mean literacy scores also have larger gaps in performance between top and bottom achievers, as in the case of Chile, Mexico and Turkey. Israel has the third-highest inequality in adult skills, following only Chile and Turkey. Japan has both the highest average literacy score and the lowest level of inequality.

In OECD countries, on average, 16% of the adult population have very low levels of literacy and numeracy, defined as scoring at Level 1 or below on both literacy and numeracy assessments (Figure 6.8). High-performing countries tend to have low levels of deprivation – for example, Japanese adults have both the highest average scores in the OECD for literacy and numeracy, and the smallest share of low achievers, at only 3.9%. Similarly, Chile, Mexico and Turkey have some of the lowest average test scores among OECD countries and some of the largest shares of low achievers – 48.2%, 46.1% and 39%.

In the large majority of OECD countries, the average PISA mathematics score for boys is higher than for girls. Although this difference is not statistically significant in many countries, girls are underrepresented among high-achieving maths students, especially in the lowest-performing countries overall (Breda, Jouini and Napp, 2018[3]). Conversely, average reading scores are consistently higher for girls than for boys (Figure 6.9) – though this gap has been narrowing over time, due to deteriorations in the average scores of girls rather than to improvements in the average scores of boys (OECD, 2019[4]).

The gender differences in cognitive skills among adults tell a similar, though not identical, story. Men’s numeracy scores (268) exceed those for women (256) in all OECD countries, with gender gaps that are usually much larger than those for 15-year-old students. Inequalities in adult literacy are more diverse: the OECD average scores for both men and women are very similar (267 and 265, respectively); women’s scores exceed those of men by at least five points only in Poland, while men’s scores exceed those of women by at least five points in seven countries.

Older adults (aged 45 to 65) perform worse on numeracy assessments (with an OECD average of 251 points) than either middle-aged (25 to 44) or youth (16 to 24) cohorts (who score 270 and 266, respectively) (Figure 6.10). A similar pattern holds for the literacy tests.

Fifteen year-old students whose parents have only attained a primary level of education perform worse on PISA assessments in reading (OECD average of 417), as compared to their classmates whose parents have a secondary (463) or tertiary (489) education (Figure 6.11). This pattern of results also holds for maths and science performance.


[3] Breda, T., E. Jouini and C. Napp (2018), “Societal inequalities amplify gender gaps in math”, Science, Vol. 359/6381, pp. 1219-1220, https://doi.org/10.1126/science.aar2307.

[1] OECD (2019), PISA 2018 Results (Volume I): What Students Know and Can Do, PISA, OECD Publishing, Paris, https://dx.doi.org/10.1787/5f07c754-en.

[4] OECD (2019), PISA 2018 Results (Volume II): Where All Students Can Succeed, PISA, OECD Publishing, Paris, https://dx.doi.org/10.1787/b5fd1b8f-en.

[2] OECD (2016), Skills Matter: Further Results from the Survey of Adult Skills, OECD Skills Studies, OECD Publishing, Paris, https://dx.doi.org/10.1787/9789264258051-en.

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