Passive investments are steadily gaining in popularity. Passive funds replicate an index and thus aim to reap a market risk premium. Active management instead allows fund managers to pursue multiple strategies that aim to achieve superior performance compared to a passive benchmark. However, these strategies usually require more trading as well as skill. Fund managers are compensated for their skill as well as for trading costs. On the one hand, active fund managers as a group underperform the market and, according to some research, investors should only invest passively. On the other hand, active fund managers may have superior information or skill that they use to their clients' advantage. The project will examine trading related to index component changes to identify whether active fund managers exploit limited passive investors. First, we aim to identify and characterize the subset of active funds that follow a potentially simple index reconstruction strategy that is not feasible for limited passive fund managers. Next, we want to calculate the costs that passive funds incur as a result of the active funds' strategy. After establishing that active fund managers benefit from exploiting passive investors in the same benchmark, we ask whether and to what extent active fund managers show skill in using this strategy.