Cognitive Ability Levels of 9th-Grade Students across Germany’s Federal States: IQB Education Trends 2009–2024 and the Role of Migration Background

Ronald Henss

Published: 2026/03/01

Abstract

The IQB Education Trends constitute Germany’s national counterpart to the PISA studies. In large-scale representative assessments conducted in 2012, 2018, and 2024, the performance of 9th-grade students in mathematics, biology, chemistry, and physics was measured, while German and English were assessed in 2009, 2015, and 2022. The present study analyses these data at the level of Germany’s 16 federal states. At this highly aggregated level, performance across subjects (with the exception of English) and across all assessment cycles is extremely highly intercorrelated and can be reduced to a single global factor termed IQ-B, which may be interpreted as an almost perfect measure of general intelligence. This factor reveals a massive performance advantage of the eastern over the western federal states. After controlling for the proportion of students with a migration background, this advantage disappears entirely while a clear south-north gradient becomes evident. The region of origin of migrants emerges as a decisive variable: immigration increasingly originates from countries with substantially lower average cognitive ability. Demographic projections indicate that the share of the ethnic German population will shrink to less than one-third by the year 2100. Continuation of current trends would inevitably lead to a substantial decline in Germany’s average cognitive ability level.

Cite this paper   Download PDF