Supercentenarians are concentrated into regions with no birth certificates
There is also the reverse process: people who are older than officially recorded.  When my in-laws came to the USA from Vietnam after the war they wanted to be able to work for a long time before anyone forced the to retire, so they just said they were 25 years old, an understatement of quite a number of years.  Upheaval and displacement tend to wipe out government records.