every so often i nostalgically visit old websites i used to maintain or frequent, and i click on all the external links to find out which still work.

has anyone done research about this? i don't know how to systemize the method exactly, but i want to know things like, "what percentage of links [over what dataset?] still work", "what are the different ways things are broken/how many in each category", "what technical/organizational decisions/circumstances impact url longevity in what ways"