OECD Social, Employment and Migration Working Papers, No. 121 The paper provides a review of literature on mismatches between workers’ competences and what is required by their job in OECD countries. The analysis suggests that over 35% of workers are over-qualified in Sweden compared with just 10% in Finland, with most other OECD countries located between these two extremes. There is also extensive evidence that youth are more likely to be over-qualified than their older counterparts and the same is found to be true for immigrant workers compared with a country’s nationals. On the other hand, no definitive evidence has been found of the persistence of qualification mismatch, with some papers showing that over-qualification is just a temporary phenomenon that most workers overcome through career mobility and others finding infrequent trantisions between over-qualification and good job matches. Across the board, over-qualified workers are found to earn less than their equally-qualified and well-matched counterparts but more than appropriately-qualified workers doing the same job. Under-qualified workers are found to earn more than their equally-qualified and well-matched counterparts but less than appropriately-qualified workers doing the same job. Over-qualified workers are also found to be less satisfied about their job and more likely to leave their work than well-matched workers with the same qualifications.