-- Is the building in a "high-risk neighborhood," which Flowers calls code for a neighborhood for poorer citizens who are much more likely to live in dangerous conditions?

-- Was the building built before 1938? The building code changed in that year, and buildings built after the change tend to be safer.

-- Is the building under foreclosure or a tax lien? "The reason those two are important is that it just speaks to the owner's financial condition," Flowers says. "I don't think there's anything revelatory in the fact that if a landlord is broke, they're going to treat their building like crap."

-- Have there been complaints? "Complaints do matter," Flowers says. "If there was a prior complaint and then a subsequent complaint six months later, it was much more likely that there was going to be a fire."

With the correct data identified, Flowers' team created a tool that was directly usable by the inspectors closest to the problem. Before inspectors had the tool, they found buildings so unsafe that they had to vacate them 13 percent of the time. Eighteen months after Flowers' project, inspectors now vacate 70 percent of the buildings.