Guest editorial Mutual fund research: a perspective on how we have arrived at the current state of academic research on mutual funds Mutual funds have existed in one form or another since the eighteenth century, although the first modern mutual fund was created in 1924. By 2016, over $40 trillion was invested in mutual funds worldwide (Investment Company Institute, ICI, 2017). No doubt, much of the recent growth in mutual funds corresponds to the demise of the defined benefit pension plan in the USA in favor of the 401(k) and other defined contribution plans, as well as similar trends worldwide. The academic literature in this area is, of course, substantial. Early work demonstrated that the benefits of active portfolio management are far from obvious (Jensen, 1968). Jensen's work laid out the methodology of measuring a mutual fund's performance via the intercept from the regression of a fund's return on a benchmark. Jensen's finding of negative estimated "alphas" raised questions about the skill of mutual fund managers and the rationality of investors. The following decades witnessed extensive work to explain when, how, and why investors should, or should not, pursue professionally and actively managed portfolios. The financial services industry responded with the launch of low-cost index funds (Hortaçsu and Syverson, 2004; Bogle, 2002, 2016) and new marketing efforts to justify active management (Jain and Wu, 2000; Chen et al., 2000). Investors responded in two divergent ways: by directing increasing wealth to new passive investment strategies (ICI, 2017; Gruber, 1996), and by investing in alternative actively managed choices, such as hedge funds (Fung et al., 2008). The continuing flow into seemingly underperforming actively managed mutual funds was a conundrum for academic researchers in the 1980s and 1990s. Financial economists attempted to explain the inconsistency by asserting the existence of potential problems with the data and methods used to measure performance (