&quot;We find that Typed Racket’s cost of soundness is not tolerable. If applying our method to other gradual type system implementations yields similar results, then sound gradual typing is dead.&quot;<p>While some of the data is surprising (22x average slowdown for TypeScript dropping to 6.5% overhead when fully typed) the paper ignores the reason why people kicked and screamed for the functionality to begin with. It had nothing to do with run-time performance.<p>Obviously the tools will improve and you can always strip out the annotations if performance is an issue.<p>Reticulated Python is still an order of magnitude faster than Ruby, so obviously performance doesn&#x27;t render a technology &quot;dead.&quot;