Stanford University researchers have published a new analysis supporting a pillar of the modern gun control movement: a prospective ban on military-style rifles commonly known as “assault” weapons.

The research from Stanford Law professor John Donohue and student Theodora Boulouta found that from 1994 to 2004, the Clinton-era federal assault weapons ban was associated with a marked decrease in mass shootings and victims of those shootings.

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As Donohue noted in a recent op-ed, not all studies have confirmed his findings. An early study from the National Institute of Justice, published upon the ban’s expiration, provided mixed results. That analysis ultimately concluded that one “cannot clearly credit the ban with any of the nation’s recent drop in gun violence,” because the number of high-capacity magazines used in crime had not decreased. The sheer number of assault weapons that had been in circulation at the time would ensure that “the effects of the law would occur only gradually.”

Donohue’s study 25 years later attempts to construct a more definitive narrative than researchers had been able to achieve in the early aughts.