Proportionately this compares quite favorably to Calment, being about double her spread from the next oldest human.
In running races, it's not uncommon for the winner to be minutes ahead of the runner-up, who is only seconds ahead of the 3rd. After they cross the finish line, several more cross soon thereafter, and then the bulk of the runners come streaming in steadily. Eventually, the bulk of the runners pass the line and we start to see stragglers who were far behind the group, trickling in one by one slowly.
The gap between Calment and #2 is over 2.5x the next largest gap in the records (1 year 80 days between #4 and #5).
Another hypothesis is that life, or genetic luck, tends to be harder on dogs than humans. Most dogs are dying as middle aged dogs, not as elderly dogs.
The oldest dog is evidently Portuguese. Not sure what that country's record keeping for dogs is like.
So anyway, in Denmark this is the standard https://www.hunderegister.dk/home dogs are tracked pretty well here.
A human born 100 years ago would have been born in 1923, I'm pretty sure the records keeping of dogs in Denmark since 1993 (when the register was established) is better than a lot of humans 100 years ago.
But sure, many of the dogs we had in the U.S nobody knew what age they really were. I am however unconvinced that just because nobody knows what ages dogs are in one region that nobody anywhere knows what ages dogs are.
There is another factor about the age of dogs that pertains as well which is that basically the oldest dog anyone knows is definitely knowable all of someones life, of multiple people's lives in the same region actually.
Obviously nobody knows what age a dog is if adopted when grown but I wouldn't be saying the dog is 23 years old if I've only known it for 20 years, I would say it is at least 20 years old because that's how long I've known it. In this I can't help but feel I'm much like most people.
Individual countries, even ones as populous with humans as China or India, or as populous with dogs as the US, don't matter for the total aggregate of record keeping. The record keeping status of an individual country is just an anecdote. It's the plural of a super-majority of the human or dog populations that become data.
> but I wouldn't be saying the dog is 23 years old if I've only known it for 20 years
People are arguing in this thread that this exact scenario happened as a conspiracy between multiple humans for Calment.
It's true that these conspiracies could exist, whether for humans, or for dogs. Bad record keeping could make it easier for dogs. Bad record keeping would also make it easier for a very long lived dog to not be recorded (though this is much less likely, as dogs over the age of 20 are something to remark on, and feral dogs generally don't live nearly that long).
the conspiracies would be more likely to have a payoff for humans though, and in the case of dogs as pointed out, all the humans that would be in charge of making a claim and that it lives among have probably lived as long as that dog or significantly longer.
As well as that there are probably lots of people who know the dog that have lived as long or longer, therefore, for any dog that it is likely somebody will make a claim about there are probably lots of people who would be able to contest the claim.
So in short, less profit, more people to dispute claims, either you have some records or you go through trouble of falsifying records for very little reason.
As mentioned by duskwuff above this could be done with a simple dog substitution (easier to do if you're breeding your own dogs), not a record falsification.
And for some people a little local fame is enough. When the substituted dog starts to get closer to the world record then the little bit of worldwide fame is just a bonus. It could even start out innocently by naming a new dog after the deceased dog. If they look enough alike any other people might not notice the switch.
I'm not saying that it has happened, just that it's possible. And that bad record keeping for dogs would make it easier to either miss very old dogs due to not knowing their age, or to substitute younger dogs for older dogs.
And for what it's worth, I live and was born in the US, but was thinking of a youtube channel that rescues animals (many of them dogs) in India, and another that rescues dogs in Ukraine.