Police officers have shot and killed at least 518 people so far this year, according to the Washington Post's database of fatal police shootings. Seventy eight people have been killed in the past 30 days. Since the start of this week, 13 people have lost their lives to police gunfire.

Police have shot and killed people on all but 12 calendar days so far this year. In other words, police shootings are basically a daily occurrence in the U.S. -- a simple fact of life when you live here. Here's how all those shootings have spread across the calendar year so far.

Last Tuesday was the deadliest day of officer-involved killings so far, with 8 people fatally shot. We haven't had a day without a police shooting since early June. On 26 days so far this year, officers have shot and killed five or more people.

Many of these shootings involved dangerous criminals. Many shootings involved suspects pulling a gun on police, or threatening the lives of other people.

But in 75 cases people were shot and killed who were unarmed, or who were armed with a toy weapon. 31 cases involved people in automobiles. Roughly 43 percent of the people shot were not armed with a gun.

It's important to know and understand these numbers, because official counts of officer-involved fatalities -- which come from the FBI -- undercount the true numbers by 50 percent or more. If we want to understand violence in America -- and how law enforcement responds to it -- we need to understand the scope of the issue.