Tennessee, Alabama and Oklahoma plan to execute inmates Thursday in what would be the first time in nearly 16 years that three people are put to death on the same day in the United States.

The executions come as a small number of states, including the three with scheduled lethal injections Thursday, drive execution numbers in the United States.

“You look at the country as a whole, you’ve just got this little pocket of five or six states that are using the death penalty, executing people, and a small number of states that are still imposing new death sentences,” said Robin Maher, executive director of the Death Penalty Information Center. Maher said it is highly unusual to have three executions on one day, although it is largely a scheduling coincidence.