Simplify the following text for a Grade 11 native English-speaking person.
Original: He became interested in the puzzle of the persistent high unemployment in Europe despite no let-up in inflation and published on this subject with Jean-Paul Fitoussi ( the director of OFCE ) .
Simplified: He became interested in the continuing high unemployment in Europe and published some work about it with Jean-Paul Fitoussi ( the director of OFCE ) .