"Judging from the spikes every decade prior to about 1800, it seems that Wikipedia generously applies birth year categories when birth decades would be more app

"Judging from the spikes every decade prior to about 1800, it seems that Wikipedia generously applies birth year categories when birth decades would be more appropriate. Nonetheless, the birth categories turns out to be far better curated than the machine-readable PersonData field." Looks like it's a Wikipedia problem.