20-year rule

20-year rule - The "20-year-rule" is a rule adopted for the validation of extreme longevity in accordance with the scientific standards for age validation. It concerns the credibility of the early life evidence. It says that a case documentation has to include at least one document issued within the first 20 years of the claimant's life. It is explained by the fact that most of the possible age changes tend to occur in the adult life, apart from a few exceptions. It has been originally introduced in the American supercentenarian study in order to enable the validation of age without the obtainment of birth record. It was due to the fact that in the United States, birth records weren't introduced in all states at the time of supercentenarians' births, but there has always been a great system of US censuses, conducted every ten years, available to the public view presently. However, the rule fits well for all regions in the modern world. The rule is of the crucial importance. Practically, the lack of a document issued within the claimant's first 20 years of life makes the validation of their age impossible and the case is to be considered as incomplete until the discovery of such. Some of the world's leading gerontology researchers say that due to possible age modifications at a very young age, an even more strict rule should be introduced, namely, the 10-year rule. This topic will remain a subject of further discussions in the scientific circles.