Posted by Ken Kurtis on October 31, 2000 at 11:37:00:
In Reply to: Re: D.A.N. Numbers (raw data) posted by Kendall Raine on October 31, 2000 at 08:54:19:
(Kendall Raine wrote) This is the problem with DAN data: it's bits and pieces, like a picture puzzle with most of the pieces missing.
Actually, that's the problem with getting ANY information out of this industry to draw any reasonably supportable conclusions. The numbers just don't exist because the companies don't release them. PADI, NAUI, et al, won't release cert numbers to give us a base. The mfgs won't release sales figures to give us a further peek at the picture. Dive shops don't share their figures with each other (although there has been a notable effort by the Leisure Trends Group, a subsidiary of Gallup, to survey stores and get some real data during the past year - Reef Seekers is a reporting store as are some others in the LA area).
Is it any wonder that misinformation is more prevalent than good information in the dive business?
When I look at the D.A.N. numbers, there's a different picture I see.
The industry assumption is that there are 2.5 million "active" certified American divers doing an average of 10 dives each per year. That should yield a total of 25 million dives per year. (And remember that the D.A.N. stats are based on Americans diving here or abroad, as well as foreigners diving in America.)
Although the PDE group may not exactly represent the demographic profile of the general diver, I'd be willing to bet it's probably close. So, for the sake of argument, let's assume that the PDE hit rate is somewhat close to that of the general diving public.
In the PDE group, 12,849 dives produced 4 hits, which yields 0.0003113 when 4 is divided by 12,849.
Using the 1999 (based on 1997 data) D.A.N. numbers, we have 820 DCS cases. If we take that numer and divine it by 0.0003113 (the presumed hit rate that proiduced the 820), it yields 2,634,115, which would be the total number of dives required to produce 820, assuming the same rate.
(Using the 2000 numbers based on the 1998 data we have a total of 431 cases, both bends and embolisms. In the 1997 data, bends represented 84% of the total cases. using that nukber for the 1998 data, that reduces our 431 to 362 bends cases. Divide 362 by 0.0003113 - the PDE hit rate, and it yields 1,162,865 dives.)
Now even though we can quibble about the accuracy of the methodology, I don't think it's going to produce an error on a magnitude approaching 10. And there's no question that 2.6 million dives is a far cry from 25 million dives.
And if the 2.6 million is somewhat representative, it might indicate that there are far fewer "active" divers than we've assumed. Or that they don't dive as often as we thought. Or maybe the 2.6 million isn't correct at all and the 25 million is closer to true, which would indicate an ever lower (1/10th as much) bends incidence in the general population as compared to the PDE group.
But the caveat this should point out to everyone, is that when ANY of us posts "data" or "facts" and starts quoting numbers, make sure you understand the source. And, IMHO, we should hold each other accountable for that. Because there's very little accurate information out there, let alone verifable numbers.
A lot of what you read here (my posts inlucded) represents opinion, instinct, and hunches. And it's important to keep all that in mind when we're trying to determine who's "right" and who's "wrong".
Ken Kurtis
NAUI Instr. #5936
Co-owner, Reef Seekers Dive Co.
Beverly Hills, Ca.