I use the cross-country and time variation in the demographic structure of 11 European countries to study how changes in cohort size affect real earnings in Europe. I find that cohort size has a negative and statistically significant effect on earnings, and that this effect is larger for the older age group—aged between 35 and 54—than for the younger group—aged 20 to 34. I also find that earnings are more sensible to changes in cohort size in Southern Europe, which points to a lower degree of substitutability between individuals with the same education but different age. I argue that the uncovered lower substitutability in the Olive Belt of Europe is in line with the higher employment protection that its workers enjoy, at least compared to the workers located in Northern Europe.