On the advice of Kim Kardashian, President Trump on Wednesday commuted the prison term of Alice Marie Johnson, a 63-year-old great-grandmother, who in 1996 was sentenced to life without parole in federal prison on nonviolent drug and money laundering charges.

It's a somewhat surprising move coming from Trump, a president who has publicly called for executing drug dealers. But Jordan's case underscores how many nonviolent drug offenders are serving life terms in federal prison. According to federal corrections data analyzed by the Sentencing Project, a criminal-justice-reform group, as of 2016 1,907 federal inmates were serving life sentences for drug offenses, which are by definition nonviolent (more on that below).

An additional 103 offenders found guilty of those crimes were serving “virtual life sentences,” which the Sentencing Project defines as sentences of 50 years or more. Under federal law, there is no possibility of parole for crimes committed after Nov. 1, 1987.

All told, drug offenders make up about 30 percent of the current population of 6,720 federal prisoners serving life or virtual life sentences. According to the U.S. Sentencing Commission, drug trafficking offenders can receive life sentences for dealing “large quantities” of drugs. But in real terms, those quantities can be small: 1 kilogram of heroin, half a kilogram of methamphetamine mixture or a little over a quarter-kilogram of crack cocaine.

Drug offenders can also receive life sentences if they have a significant criminal history or if prosecutors can demonstrate that bodily injury or death resulted from the use of the drug.

While buying and selling drugs on the black market is, strictly speaking, a nonviolent activity, the illicit drug trade is implicated in tens of thousands of deaths each year. Drug reformers point out that much of the death and destruction associated with the drug trade stems directly from the drugs' illicit status.

At an average annual cost per inmate of roughly $32,000, it costs American taxpayers about $64 million a year to imprison the 2,010 drug offenders currently serving federal life or virtual life sentences.

According to a report from the U.S. Sentencing Commission, a total of 64 life sentences doled out by federal courts in 2013 — more than 40 percent of all federal life sentences — involved drug crimes as the primary offense. More than half of federal life sentences for drugs involved cocaine or crack cocaine that year. There were four life sentences for heroin and another four for marijuana. Nineteen offenders received life sentences for methamphetamines.

It's worth pointing out that the number of federal inmates serving life or virtual life terms is dwarfed by the number at the state level, where most criminal justice enforcement occurs. In 2016 there were 6,720 federal life offenders but nearly 200,000 with life sentences in state prisons, according to the Sentencing Project.

Presidential pardons apply only to federal crimes, making them of limited utility for addressing the nationwide problem of over-incarceration. If Trump were to pardon every one of the 6,720 federal inmates currently serving life or virtual life sentences, it would reduce the total population of American inmates with life sentences by 3.3 percent.