For all the detractors of the EMH - the Efficient Markets Hypothesis - and for all its fans, as well as for any fan of economic history, this paper is a must-read: http://www.terry.uga.edu/media/events/documents/Newhard_paper-9-6-13.pdf.
Back in 1954, an economist, Armen A. Alchian, working at RAND conducted the world’s first event study. His study used stock market data, publicly available at the time, to infer which fissile fuel material was used in manufacturing highly secret H-bomb. That study was immediately withdrawn from public view. The paper linked above replicates Alchian's results.