This chapter presents and compares results from two studies that analyse the same research questions with different data sets. The first study analyses data on productivity at the level of work teams in one single plant. The tasks in this plant are rather homogeneous and age-productivity profiles can be estimated fairly precisely. But the results cannot be generalized to other parts of the economy. The other study analyses the Finnish Linked Employer Employee Data (FLEED), which provide information on productivity at the plant level for the Finnish economy. At this aggregate level, age-productivity profiles are obviously cruder. On the other hand, the results apply to a large part of the entire Finnish economy and can easily be generalized to other developed economies. The linked data also make it possible to compare productivity and wage profiles by age.