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Exchange-traded funds (ETFs) are one of the major financial innovations of the last thirty years. And yet, it is only recently that academic research has started to embrace this topic. This paper examines the reasons behind the time lag between the launch of ETFs in the 1990s and scientific output on these instruments. Our analysis suggests that the development of academic research has closely followed, but with a significant delay, growth in the number of listed ETFs, their assets under management, and the first critical events questioning their apparent simplicity and safety.