That's probably the assumption they're working with, because historians do it all the time. Document survival for the pre-modern period is so poor that it doesn't take very many examples to demonstrate (for all intents and purposes) that something was widespread.
That's probably the assumption they're working with, because historians do it all the time. Document survival for the pre-modern period is so poor that it doesn't take very many examples to demonstrate (for all intents and purposes) that something was widespread.