The Relationship Between Lead Contamination and the Word 'Lucifer'

This episode features Rick Nevin, an economist who is known for his research suggesting that lead is one of the main causes of crime. Rick and Julia discuss: how do we know the correlation between lead and crime is a sign of a causal relationship? Has the lead-crime theory made any successful predictions? And is it possible that getting rid of lead could reduce the crime rate down to zero?