In an exhaustive 10 year survey, the NBER show that Active Managers have delivered value to their customers. However, they also show that this value is being eroded as ETFs look to replicate the mainly "smart beta" strategies that have delivered such value.
Asset managers who actively manage large institutional investments outperformed benchmarks by 42 basis points after expenses, according to Asset Managers: Institutional Performance and Smart Betas (NBER Working Paper No. 22982). Researchers Joseph Gerakos, Juhani T. Linnainmaa, and Adair Morse estimate that they achieved this through "smart beta" strategies, which weight portfolios to track various factors and indices that have historically earned abnormal returns.