LAWRENCE — More than 1 million rape cases have gone undocumented across the United States during the past two decades, according to research by a University of Kansas law professor. The chronic under-reporting happened during what was widely considered a “great decline” in violent crime.

Corey Rayburn Yung, associate professor of law, has authored “How to Lie with Rape Statistics: America’s Hidden Rape Crisis.” The article, which will appear in the Iowa Law Review, details Yung’s review of crime data from 1995 to 2012, which shows that by conservative estimates, nearly 1.2 million rapes disappeared from the official record. Yung analyzed data from the FBI’s Uniform Crime Report, which collects data from nearly every police department in the country, and is commonly used by policy makers, media and law enforcement as a picture of crime prevalence in the United States.

Yung has taught and conducted research in rape and crime law and noticed inconsistencies in the number of rapes reported in a number of cities. Raw numbers of rapes were much lower in some cities than raw numbers of murders, which raised red flags as murder is a less common crime. Yung then learned of media investigations in Baltimore, New Orleans, St. Louis and Philadelphia that documented cases of police departments under-reporting rape statistics.

“Originally I was trying to reconcile why the data was showing such anomalies,” Yung said of the impetus of his paper. “Then I found out about the four cities with documented cases of under-reported rapes, and the more I looked the more red flags there were. There were a number of cities where the numbers didn’t make sense.”

In all, 46 cities, or about 22 percent of the 210 studied police departments responsible for populations of at least 100,000 people, had “substantial irregularities in their rape data, indicating considerable undercounting from 1995 to 2012,” Yung wrote.

“Many people have an incentive for crime to be down on paper,” Yung said of the reason why rape numbers were under-reported.

Pointing to reduced crime numbers, politicians are often elected or re-elected, policy makers make decisions on police funding, officers are promoted, communities promote themselves as safe, and numerous other decisions are made. There is intense pressure, politically and socially, for police departments to show they are reducing crime.

“From a personnel perspective, every officer has a reason to downplay the numbers,” Yung said.

Rape happens to be one of the easiest crimes to under-report, for a variety of reasons. There is a very low conviction rate — only about 2 percent — for all rapes. That manifests itself in fewer cases coming to trial as they are viewed as harder to win, and less time and resources being invested in investigations. There is also often very little corroborating evidence that a rape occurred. In crimes such as murder there tends to be a litany of forensic evidence, and it’s obvious a life has been lost. In less severe crimes such as auto theft, there is an insurance claim that must be dealt with. In the case of rape, there is often not a rape kit, and an alarmingly high percentage of the time when there is one, it is never processed and any evidence it might contain is not used as part of an investigation, Yung said. In cases where drugs or alcohol made consent impossible, drug tests are often not performed in time, and even when they, are they don’t always test for all relevant drugs.

“If you wanted to manipulate a crime rate statistic, that’s the easiest one,” Yung said of rape statistics.

Yung’s article states police in the undercounting cities used three difficult-to-detect methods to manipulate rape statistics: Designating complaints as “unfounded,” which required little or no investigation; classifying incidents as a “lesser offense"; and failing to create a written report that a victim made a rape complaint. In addition to the four cities exposed by media reports, Atlanta, Dallas, Milwaukee, Mobile, Ala., Oakland, Calif., and Washington, D.C., submitted statistically dubious rape statistics in 92 of their 108 total reports to the FBI during the study period, Yung wrote.

By including the estimated number of rape incidents reported to police but not the FBI, Yung conservatively estimated that approximately 796,213 to 1,145,309 rapes were not included in the Uniform Crime Report from 1995 to 2012. The analysis indicates that the study period included at least 15 of the 18 highest rates of rape since the Uniform Crime Report began including rape data in 1930.

Rape complaints that are not investigated not only fail to serve justice for victims, they lead to more victims and impunity for criminals, Yung argues. Research has suggested that as many as 90 percent of rapes are committed by serial rapists or individuals who have committed the crime more than once.

“That gets validated when they’re not investigated,” Yung said of the perpetrators. “They can do it again and again. Police are essentially empowering rapists by not pursuing cases.”

There is little recourse for rape victims in many cases. If their complaint is determined “unfounded” or is never investigated, it is very difficult to take any sort of action without surrendering their anonymity. On top of that, most victims are never notified that their case is not being investigated.

While the FBI’s Uniform Crime Report is highly influential, it’s nature also contributes to the frequent under-reporting of rape. Police departments offer all information included in the report voluntarily, and there is little to no disincentive for not including complete and accurate statistics while there is overwhelming incentive to under-report, Yung said.

The implications of under-reporting are dire. Many rapists are never convicted, much less prosecuted or even investigated, leading to more rapes and more victims, Yung said. When left unchecked, the incidents can escalate to further violent crimes and even murder, which have troubling moral implications.

“Society has an obligation to stop rape and prosecute rapists. The current practices are incredibly far from that basic precept. What is worse is that the extent of rape in America has been covered up— rape victims have been denied basic dignity, so that some police could manipulate statistics to simply achieve artificially designated crime benchmarks,” Yung wrote.

While reports of a “great decline” in rape in the United States were untrue, the crime grew to crisis proportions that should urge everyone from city level government to federal policy makers to act. Yung suggests the FBI expand oversight of data submission for the Uniform Crime Report and training of police officers in using it. The bureau should also take action when departments report unprecedented decreases in rape while murder rates spike, a step it currently doesn’t take.

“Rape has not received significant priority in law enforcement, as crime data has lessened the perceived urgency for action. That can and should be changed with budgetary, resource and personnel increases from the federal and/or state authorities,” Yung wrote. “Local governments and police departments should allocate more of their existing officers to sexual assault investigations instead of low-level, nonviolent crimes. Further, police should implement secondary review of rape complaints to ensure that officers are thoroughly investigating cases labeled as 'unfounded' or similar internal department designations that have in the past disguised large numbers of rape cases.”