How many accidents per year are results from trampolines?

I'll interpret "accidents" as those resulting in a fatality, and restrict my answer to the USA. In the United States we can go for multiple years without a single tandem fatality. That said a couple of years ago we had two students fall out of the harness. As a result, harness design were modified, and older design harnesses taken out of service, also efforts were made to reassure that instructors were properly adjusting the student harnesses. In the last ten years or so there have also been a couple of double tandem fatalities (both instructor and student).