To be honest, it wasn't hard to find. '1.3 100,000 caa' and '1.14 100,000 faa' in google work fairly well.
, quite.
In the same paragraph of the UK document where we find the ratio you dug up, we read:
Meaningful comparison of the UK data with other foreign States was not possible due to differences in the definition of GA and a lack of available information, particularly utilisation.
and a few sentences down...
However, the estimated FARs for the various classes of UK GA were found to be [...] better than the rate for most European States.
which is quite a statistical find, in view of admitting they're comparing apples to oranges and that they are only doing a survey once in a blue moon.
The UK CAA definition of GA is "anything civil that is not a CAT operation"
whereas other states use : GA = light aircraft (under 12500 lbs) or some other definition.
The UK CAA also don't say how they measure/estimate "hours flown", which is of course the denominator of your accident ratio, just that it is "constant" at 1.4 million hours. They are also not clear about counting the N-reg hours in the UK, which inevitably would drive their accident rate down.
By comparison, General Aviation in the USA had 1518 accidents for about 23.8 million hours flown in 2006, or about 6.3 accidents per 100000 flying hours. The 2006 number of fatal accidents per 100000 flying hours was about 1.1
It should be noted that the US have something out there like Alaska, which due to the harsh flying circumstances (and living conditions) distort the US result somewhat.
US references all on
www.faa.gov (search) with very detailed materials on methodologies, statistical errors and a great many additional indicator...
Although the data presented doesn't statistically support it, the UK accident rate might actually be better than the continental european one if only for the existence of the IMC rating. A similar recognition was made by EASA in its introductory comments about FCL.008 (the accessable instrument rating). The same argument could then explain why the UK has a slightly higher GA (fatal) accident rate than the US.