Supercentenarians are concentrated into regions with no birth certificates
While I've also congettured in the past that at least a good chunk of extreme supercentenarians  are due to anagraphical errors if not outright fraud, I do not think that the paper support the thesis well.<p>For starter they do not have a global model, it seems that they handpicked different statistics for different areas that support their thesis (they do not even show anything concrete for Japan).<p>Regarding Sardinia, their numbers seem actually wrong: looking at the raw Istat data the numbers for 55 year life expectancy for the Sardinian provinces seem in line with the rest of Italy (95-96%) putting Sardinia somewhere in the middle of the (quite tight) Italian distribution.<p>It is possible that the researcher averaged the data over a longer period of time that I bothered to look is possible, but the paper doesn't discuss the methodology.<p>Their fitting, p value not withstanding, also seem a bit adventurous; the fact that all and almost only Sardinian provinces are extrme outliers shoud have been a tell. The rest of the Italian bprovinces are in a tight uniform cluster.<p>Sardinia, except for a very brief period in the mid 2010s,has only 4 provinces, so it is possible that messed up their data extraction (they show 8 provinces).<p>Also Sardinia is not particularly poorer than the rest of Southern Italy and actually has a lower crime rate (which they suggest but not outright state is a factor).<p>A better paper would probably try to build a single model for Japan, Italy and US using actual mortality, crime and poverty rates.