Excellent link, SansAnhedral, thank you!
The FAA's General Aviation and Part 135 Activity Survey: In response to a public records request made by The Times, the FAA provided a decade of its annual estimates about the activity of America's most common helicopter models. This data is not published online.
Ah, this explains why the data is so hard to get. I actually called the FAA, but no joy. I should have done a FOIA request!
In an email to The Times, Robinson Helicopter Company President Kurt Robinson said he believed the FAA survey underestimates the R44's flight hours. He wrote:
Please note, the fatal accident rate of 1.61per 100k flight hours used to compare the R44 with other model helicopters from 2006 to 2016 does not reflect the actual usage rate of the R44 helicopter. Your estimated flight hours are based on the FAA General Aviation Survey, which is a voluntary survey and more representative of larger commercial operators, not the U.S. helicopter industry as a whole. Robinson’s own calculations, based on R44 production, overhaul records, and time-in-service reports, conservatively estimate total flight hours to be 3,260,787 hours, 38% more than the FAA estimate.
I find this totally believable. I'm one of the many operators who gets that survey and can't be bothered to complete and return it.
That still puts the R44 at the top of the list at 1.16/100K, but not so dramatically.