How common are skydiving accident deaths? Not very.

Three men have been killed in skydiving accidents in Massachusetts this year, highlighting the risks of what many consider to be a dangerous sport for thrill seekers and adrenaline junkies.

In mid-August, Daniel Pelrine, a 37-year-old Mattapan iron-worker, plummeted to his death in Pepperell, after having made hundreds of skydiving jumps. On Sunday, Andrew Munson, 29, of Nantucket, and his instructor, Eldon Burrier, 48, of West Lynnwood, Wash., were killed during a tandem jump.

In 2013, there were 3.2 million jumps out of airplanes in the United States, and only 24 people were killed in the process. That’s a death likelihood of about 8 in a million jumps, which is one of the lowest death rates in the sport’s history, according to the US Parachute Association.

The rate of people dying in skydiving accidents has declined steady since the 1970s, the association reported. The average number of yearly fatalities during the 1970s was 42, compared to 26 during the 2000s and 22 since 2010.

Between 2000 and 2013, the number of fatalities per year decreased 25 percent.

What’s more striking is that the rate of skydiving deaths decreased by 37.5 percent. That’s as more Americans choose to jump out of planes; the number of annual jumps increased by 18.5 percent since 2000.

Tandem skydiving is said to be even safer. The US Parachute Association reported less than 0.003 student fatalities per 1,000 tandem jumps over the past decade.

While skydiving is getting less risky — due, in part, to increased regulation and safety considerations, according to the US Parachute Association — it is still the act of jumping out of the plane and therefore, is not without danger.

The Federal Aviation Association and local law enforcement agencies are investigating both Massachusetts fatal skydiving incidents to determine what went wrong during the jumps.