Just a quick question that I'm sure has a simple answer- how do they come up with the average life expectancy in dogs? Where do they get their data from?

Mainly observation and experience. Vets have data, and the KC did a breed survey some years back.

Well I am not sure that you can, you need to know the age at death of dogs of that breed less those who died from an injury of in something like a fire - you then add all the ages up and divide by the number of dogs and that gives you the average age at death. But you would need a number of dogs related to the number born over say the last 5 years at the very least, one would think that a length of time that was say twice the expected age at death would be needed for an accurate average. Hope the breed you are interested in is not one of high numbers (grin)

I would think then, that surveys on age of death in breeds would need to be carried out fairly regularly. My last two GRs were older then the average, the first one was about the average (then). My assumption for increased life spans now is better veterinary care and improved foods.

I don't entirely believe that they have improved.  I wish that the KC would allow us to be able to put Date of Death on the database that people view.  I think that would be really handy as well as being able to see health results etc. 

Yes the Scandinavians, at least the Finns on Koiranet do have dates of death (assuming the owner notifies).

Nova I think they take all deaths (accident etc included) when working out lifespans, at least in the KC survey they did.

Must say of the three I have loat two have reached or gone over the average (13 years 5 months) one at 13 years 7 1/2 months, one at 13 years 10 months, but sadly  one at just 11. 

All three were fit and active to the end suffering no geriatric issues, the younger oen died of natural causes the otehrs were put to sleep, after sudden illness.  I do have to say I am not the kind of owner to prolong life for the sake of it.

I think a date of death would be a great help, it's certainly something I've been looking at, or trying to, to help me decide on a breeder for my next dog.

May breeders will have the dates on their website, I do for my deceased girls.

You can of course ask the ages they have lost their dogs and those they have bred.

Dogs I have bred who have let me know have all lived 12 - 15 years.

I think there is so much more involved in longevity than genes, when you think about it at the very basic level there are those that hang on to their dogs to the very last bitter moment and others that call it a day once the dog shows permanent discomfort. It is almost impossible to factor in lifestyle as it is to include the result of infection, allergens and medication. If the length of life is really that important to you then I think looking at the average life a a particular line would give a better idea than looking at a breed average.
Most of my present breed have reached the breed total and then some and the last was on the way to 15 but my GSD's apart from one who died at 9 were all over the average then stated, I have never had one die naturally I have always had to decide to call it a day on their behalf, so my dogs would distort the average if we are looking at a natural death.