Is Krugman reading this blog?
Not likely. More probable is that human thought shares itself via Teilhard de Chardin's theory of the "noosphere." As consciousness and complexity grows, people unknowingly inhabit a common thought-space.
Long ago I once had a marvelous idea for a music player than could be used while the listener was doing laps in the pool. I made sketches of the devise and was about to go the next step. Two weeks later Sony announced plans to sell such a devise. I don't recall reading or hearing about it before then. I am sure good (and bad) ideas pop into lots of heads at around the same time.
[Photo: Wallace Adams-Riley, https://www.facebook.com/wallace.adamsriley?ref=ts]