"The removal of lead from all petrol, then, should usher in a Golden Age. In America, since the ban of 1996, researchers estimate that IQ scores have risen by several points and 58m crimes have been avoided."

AS THE fascinating obituary in The World in 2013 points out, this is the year in which our cars will no longer—according to a rather hopeful deadline set by the United Nations—be powered anywhere in the world by leaded petrol (or gasoline, as Americans prefer to call it). All of which will be very good for world health. As the obituary says:

The removal of lead from all petrol, then, should usher in a Golden Age. In America, since the ban of 1996, researchers estimate that IQ scores have risen by several points and 58m crimes have been avoided. The spread of peace to some of the world’s more benighted countries may happen not because leaders parley or Western troops leave, but because the element of wickedness has been taken out of their cars. In so far as lead survives, it will no longer be in forms that can be widely ingested or inhaled.

It seems obvious enough that when a brain-affecting toxin is removed, IQ scores will improve. But what Cassandra finds more interesting is the idea that "58m crimes have been avoided". Is this true, and how can we possibly know?