Clinton,
I would make the following comments:
For example, if your observations about the GAAP MAC sample size and the consequences for the conclusions that may or may not be validly drawn from the data are correct, there is no valid basis upon which to compare Australian and US MAC rates.
In the context of the Ambidjii report, they are effectively saying that 350 or so US Class D zones are operating at an intolerable level of risk. Quite apart from any FAA/AOPA/FSF view on that matter, the aviation insurance underwriting sector does not see it that way, either.
In my opinion, only broad generalizations can be drawn by comparisons, such as (unsurprisingly) that collision risk is greater in the circuit area than en-route (despite a in my opinion hilariously inept study by Airservices, that neglected the fact that most of the US mid-west is around 5-6,000 ft AMSL).
However, MACs are rare enough in US that they too can be looked at individually.
The major conclusion I draw: that MAC is not a major cause of incidents or accident, given the "big picture", but looking at the Australia reaction to matters airspace, that are entirely uncontentious in just about any other country, one could easily get the impression that MACs were the biggest air safety problem in Australia.
In about March 2002 (or thereabouts, give or take about a year) US FSF did an interesting study on Australia's air safety record, every Australian pilot, LAME and ATC should read it.
Yet some people seem to have no compunction in extrapolating Australian accident/incident rates and concluding that Australia has a higher accident/incident rate than the US.
One of the problems we have here, is the belief that Australia has the world's best air safety record, a severe case of "rose coloured glasses". We are fond of quoting "jet fatalities", and can't even get that right, we have had one, wiped out most of the Mareeba Council, but we confine ourselves to "RPT" jet, and pat ourselves on the back. Selectively narrow down the definitions enough, and the record will always be perfect
Given the size of the whole Australian fleet, provided you don't overdo it, a study of the Australia accident and incident rates is instructive. As far as I am concerned,
ICAO categories should be used, but we fiddle with that, too, to produce "more flattering" figures.
Some time ago, a study was commissioned, using well known insurance co. investigators, and independent (of underwriters and the aviation sector) statisticians. The then Minister had the whole paper checked by the US NTSB, who concurred with the results, including the caveats as to the limitations of interpretations.
The results, overall and in individual categories, did rather lift the rose coloured glasses for that Minister.
Prorata, GA came out the best of the categories vis a vie USA, the RPT accident and incident rates were not good. Australia did come out better than "JAA" countries. CIS states and Africa (except SA) were not included. I have no reason to believe, based on the record since, that we have significantly improved. Most of the "apparent" improvement in recent years is just that, apparent rather than real, a change in the balance of who is doing what within categories.
I'll leave experts like Ian to grapple with the issue, but I understand, from a number of experts in the area, that the number of hours/miles flown by Australian aircraft is still so small as to still be statistically insignificant.
There is an interesting paper that is a contribution to the current Aviation Green Paper, saying exactly that. It has been suggest that the loss of a single B737NG would catapult Australia from "the best" to close to the worst.
There are no shortage of individual airlines that have more high capacity transport aircraft that all operators in Australia combined, who have excellent accident/incident records.
In my opinion, just about the biggest threat to air safety is complacency, there is no shortage of complacency in the areas at which I am looking.
Tootle pip!!
Late PS: The differences in accident with the US/Australia study mentioned above were so great that no amount of Australian/CASA "rationalization" about errors/incompleteness of US data collection could explain away the differences.
There was NO category where Australia equaled or bettered the US.
What really surprised me was how bad the western Europe/UK figures were, leading to the obvious connection between draconian regulation and air safety outcomes ----- is there a proportional relationship with the volume of regulation and the accident/incident rate. Again, Africa excluded.
The greater the regulatory burden, the greater the accident rate ----is almost a valid conclusion from the public databases.
If the US consistently produces the world's best air safety outcomes, in all categories (and they do --- have a really good look at 20 year running averages) what are we, or the UK CAA, etc., achieving, except running aviation into the ground.