There remains a factual question as to whether the number of each candidate's royal ancestors or percentage of "royal blood" can be accurately estimated without being able to trace every branch of the candidate's family tree for an indefinite length. However, the relevance of such descent is also questioned due to the relatively small degree of inheritance a person receives from such distant ancestors. For instance, a person ten generations removed from a royal ancestor would have less than one thousandth of that ancestor's DNA and this amount would be halved with each subsequent generation. Thus, even if being a twenty-seventh generation descendant of King John could confer some advantage on a presidential contender, it is unclear how it would have any measurable effect.