Handguns shown in 2015 in the gun library at the National Tracing Center of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives in Martinsburg, W.Va. (Jonathan Ernst/Reuters)

The much-discussed spike in homicide rates between 2014 and 2016 is due almost entirely to gun homicides, a Wonkblog analysis of federal homicide data reveals.

The spike was so drastic that in 2016, gun homicides accounted for a greater share of all homicides than at any point in the federal record, which contains more than 80 years of complete data for the United States.

The numbers underscore how the violent-crime problem is, now more than ever, a gun-violence problem. After years of record sales, firearms are more prevalent in society than at any time in recent history. The high number of civilian guns in circulation means more opportunities for guns to be diverted into the hands of people at risk of harming others with them, potentially altering the landscape of American crime.

To arrive at the numbers above, Wonkblog compiled more than 100 years of federal homicide statistics, stretching back to the year 1910. These figures are collected by the Centers for Disease Control and Prevention as part of the National Vital Statistics System (NVSS), which compiles mortality data — including data on homicides — each year via death certificates. Note that in the years before 1933, the NVSS did not collect death certificate data for all states. The share of the total population covered in the pre-1933 data ranges from 51 percent in 1910 to 95 percent in 1932.

Historically, gun homicides have accounted for a little over 60 percent of total homicides. But that figure hasn't always been constant. The chart shows the raw numbers of gun and non-gun homicides going back to 1910. These numbers aren't adjusted for population, because we're interested primarily in looking at the relationship between the two, rather than their relationship to the total population.

The data shows that gun homicides have always surpassed homicides by other means — stabbing, strangulation, etc. — in number. In some years, as in the 1940s and ’50s, this gap is fairly small (note also the spike in non-gun homicides in 2001, the year of the Sept. 11 terrorist attacks). But in other periods, like the 1920s, ’30s and the latter half of the 20th century, the number of gun homicides soars, relative to the number of other homicides.

Particularly interesting is what's happening at the right-most edge of the chart in the present day. Since 2014, the number of non-gun homicides rose by less than 2 percent, from 4,864 in 2014 to 4,947 in 2016. But during those same two years the number of gun homicides rose by more than 30 percent, from 11,000 to well over 14,000.

Put another way, guns alone accounted for nearly 98 percent of the observed homicide rate increase between 2014 and 2016. All told, in 2016 gun homicides made up 74.5 percent of all homicides in the United States — the highest share in well over 80 years of complete federal data.

Guns' share of total homicides has surpassed 70 percent only twice before in the past century — in the early 1920s, at the start of Prohibition (when the federal data covered about 80 percent of the population), and in the early 1990s, at the peak of that decade's crime wave. During both of those eras, the total homicide rate approached 10 deaths per 100,000 or more. The current spike in gun homicides relative to other homicides is unique, in that it's happening during a period of relatively low homicide rates (6 per 100,000) overall.

It's difficult to ascertain what exactly the jump in the share of gun homicides says about our present moment. At the household level, surveys show that rates of gun ownership have remained relatively stable in recent years or declined slightly, depending on the data source.

However, there is widespread agreement that the total number of civilian firearms in circulation has recently skyrocketed, particularly during President Barack Obama's administration. The great proliferation of firearms means that more guns are being diverted from legitimate uses and onto the black market, where they end up in the hands of people who may otherwise be prohibited from owning them.

Regardless, the data above shows that since the early 1990s, non-gun homicides have seen a steady decline in terms of raw numbers and rates with the exception of the year of the Sept. 11 attacks. Gun homicides, however, have been much more volatile, with several periods of increase and decrease.

The spike in gun homicides in the last two years could simply be a more extreme case of that volatility. Or, it could be an inflection point, indicating that firearms have become so numerous in society that they're more readily available than ever to people wanting to do ill with them. If that's the case, we might expect to see gun homicides continue to increase even as other forms of homicide become more rare.