After Ferguson, a noticeable gap in criminal-justice statistics emerged: the use of lethal force by the police. If the FBI can't tell how many people were killed by law enforcement last year, asks The Atlantic, what other kinds of criminal-justice data are missing? Bruce Western, a professor of sociology at Harvard University, cited the racial demography of arrests and criminal records. Current prison statistics give a good sense of the size and scale of mass incarceration, but they provide little information on conditions inside U.S. Perhaps the most glaring gap is solitary confinement. No one knows exactly how many people are currently kept in isolation. Another major gap is the number of non-sexual assaults behind bars. Although Congress mandated the collection of sexual assault statistics with the Prison Rape Elimination Act, prisons are not required to report ordinary assaults to the Bureau of Justice Statistics.
“We have anecdotal evidence and some data in individual states that violence is rising in prisons, but we don't have good, national database collection on that,” said Marie Gottschalk, a professor of political science at the University of Pennsylvania. One prosecutorial tool with little transparency is plea dealing. In 2013, more than 97 percent of all federal criminal charges that weren't dismissed or dropped were resolved through plea deals. State-by-state totals are incomplete or unavailable, but often estimated to be similarly high.) In the absence of reliable statistics, anecdotal evidence often fills the void. This is especially true when studying racial bias in the prosecutorial process. Prosecutors are not required to compile data on racial disparities. They have little incentive to gather and publish it voluntarily, partly because of resource constraints and partly because of its potential negative implications.