Theory of interstellar trade (1978) [pdf]
I heard about this from this Odd Lots podcast: <a href="https://www.bloomberg.com/news/articles/2023-08-11/paul-krugman-on-why-alien-invasions-are-inflationary-transcript?srnd=oddlots" rel="nofollow noreferrer">https://www.bloomberg.com/news/articles/2023-08-11/paul-krug...</a>