A year ago, U.S. regulators were spooked by a burst of rapid-fire trading in Treasuries. Over a 12-minute span that morning, the yield on the benchmark 10-year Treasury note plunged from 2.02 percent to 1.86 percent, then just as quickly shot back up. Treasury yields had fluctuated that much only three times since 1998, and each of those times there was an obvious catalyst. This time, there was no apparent cause.
The U.S. Treasury Department and four other federal agencies that oversee slices of the bond market began to look into what had happened. Nine months later they released a report laying out a reconstruction of Oct. 15, 2014, that contained enough of a dissection to impress even some high-speed traders who had been doing their own analysis. Still, for all its hard work, Treasury failed to fully answer the most important question: Who or what caused the wild price swings?