A knowledge spillover is when someone thinks up a new idea, that might be more valuable privately if it didn’t spillover into public use.
If the alphabet had been copyrighted, would it be used as much? Probably not, and that would be a bad thing. The thing is, someone is less likely to invent something in the first place if they can’t prevent or control those spillovers.
Good answers — about whether we’re better off protecting the rights of inventors to profit from their inventions, or better off letting society get stuff for free — are hard to come by. Macroeconomists do make primitive measures of this sort of thing, which tend to suggest that we protect inventors too much.
From the July 26, 2012 edition of Frank and Ernest.