Two men who randomly joined demonstrators protesting the shooting death of Michael Brown kneel in the intersection as they confront police officers in riot gear November 30, 2014 in St. Louis, Missouri. (Joshua Lott/Getty Images)

YOU CAN’T make good policy on the basis of bad information — or no information at all. Among the lessons of the tragedy in Ferguson, Mo., is that, when it comes to the realities of policing their cities and suburbs, many Americans did not know how much they did not know.

In addition to the learning that’s taking place about racial disparities in law enforcement, there is also a sense of surprise at what the federal government had been doing prior to Michael Brown’s death to make relations between communities and the police better — or worse. Perhaps nothing was more eye-opening than the spectacle of protesters squaring off against local police using military weaponry and armored vehicles, much, if not all, of it supplied by Washington. Before Ferguson, “police militarization” was the relatively arcane concern of civil libertarians; after Ferguson, it’s practically a cliche.

So there was cause for both encouragement and disappointment in the response to Ferguson that President Obama unveiled Monday. Insofar as it addressed charges of police militarization, Mr. Obama’s announcement offered a welcome dose of information, in the form of a report showing that the Defense Department’s “1033” program, local police forces’ main source of surplus military equipment, has transferred 92,442 handguns and rifles, 44,275 night-vision devices, 5,235 Humvees, 617 MRAP armored vehicles and 616 planes and helicopters in recent years.

None of this equipment was supplied in meaningful coordination with other, similar federal programs, according to the report; nor does the Defense Department “review how equipment is being used.” Stunningly, when police agencies acquire this materiel, “[l]ocal elected officials are frequently not involved in the decision-making.”

Mr. Obama seeks to remedy that by requiring civilian input and by compiling more information about how police use the equipment they obtain. Those changes, to be embodied in an executive order, are welcome. He balked at more substantial reforms, however, such as bipartisan proposals on Capitol Hill to limit military equipment transfers. It’s going to be up to Congress to rein in the flow of military equipment, in the face of what is already strong lobbying from police unions and others. The president did propose $263 million in funding for police training and community policing, the most important aspect of which was $75 million for body cameras for officers. That could be enough to put a video recording device on 50,000 police officers — or less than 10 percent of the total working in cities and suburbs.

Cameras could bring more transparency to police work, deterring violence by both officers and civilians and rendering more accurate any investigations of violence that does occur.

Left out of the president’s proposals, though, was any mention of a systematic clean-up of the federal government’s data on police use of deadly force, the completeness and accuracy of which remain decidedly unsatisfactory 20 years after Congress passed a law intended to track such incidents. To this day, no annual report provides authoritative data on killings by police and the circumstances in which they occur. That’s the kind of truth that the federal government is uniquely equipped to seek, and to tell.