How police interact with black men is in the news again following the April 19 death of Freddie Gray in Baltimore.

One of the more popular fact-checks we did followed the 2013 acquittal of George Zimmerman, a volunteer neighborhood watchman who shot and killed Trayvon Martin, a black Florida teenager. Since this fact-check is a perennial reader favorite, we wanted to update it with more recent numbers.

Here is the statistic we fact-checked from a tweet:

"In the 513 days between Trayvon dying, and today’s verdict, 11,106 African-Americans have been murdered by other African-Americans." We rated the statement Mostly False because the number was a rough guess. That tweet related to data about race and murder in 2005.

Also, experts told us that most people -- whether black or white -- are murdered by people in their own racial group, and that has held true for decades.

From 1980 through 2008, 84 percent of white victims were killed by whites and 93 percent of black victims were killed by blacks.

Let’s look at the numbers for the most recent years using the FBI’s annual Crime in the United States reports:

Percentage of blacks murdered by blacks Percentage of whites murdered by whites 2009 91 84 2010 90 83 2011 91 83 2012 91 84 2013 90 83

There are some important caveats about these numbers -- most importantly is that they don’t include every murder. The data only reflects murders that involved a single victim and offender and when the race of the offender was known and reported by police to the FBI.

Due to those shortcomings, Northeastern University Criminology Professor James Alan Fox modified the FBI data files to estimate the characteristics of unsolved homicides and unreported cases. Fox’s data shows that the majority of people are killed by someone from their own race. For example, for 2010-13, his data showed that about 92 percent of blacks who were murdered were killed by other blacks, while the statistic for whites killed by whites was 81.5 percent. That is very close to the official numbers.

Why do the murder statistics show this pattern? Well, people tend to marry, date, befriend and live with people from the same race. So it’s not really a surprise that people are usually murdered by someone from their own race.

"People tend to be murdered by those who know them," Fox said.

And even in murders where the victim and offender don’t know each other, there still is a race correlation.

"Because of the racial homogeneity of most neighborhoods, moreover, it is even true that most stranger killings are intraracial — 67 percent for white victims and 89 percent for blacks" based on data between 2000 and 2009, Fox wrote in his book The Will to Kill: Making Sense of Senseless Murder.

Overall, the percentage of homicides that cross race lines has increased from about 8 percent of the total three decades ago to about 13 percent of the total, Fox wrote.

"This increase does not necessarily reflect growing levels of racial hostility; it could also reflect increased contact between black and white Americans in everyday activities, including work, school, and romantic relationships," he said.