(The Wall Street Journal Europe) Pont L'Abbe, France -- Trader Jerome Kerviel and his brother grew up on a cul-de-sac near rocky potato fields. Their mother cut hair in a low-rent beauty salon off a parking lot. Their father hammered metal into bed frames in a cinder-block workshop.

The last time anything really exciting happened in this windswept corner of northwestern France was back in 1961, when local potato farmers angry at slumping prices went on a violent rampage. The brothers Kerviel missed that. Jerome was born in 1977, his brother, Olivier, seven years earlier.