I can't get over this...

An excerpt from the book Freakonomics:

Some cheating leaves barely a shadow of evidence. In other cases, the evidence is massive. Consider what happened one spring evening at midnight in 1987: seven million American children suddenly disappeared. The worst kidnapping wave in history? Hardly. It was the night of April 15, and the Internal Revenue Service had just changed a rule. Instead of merely listing each dependent child, tax filers were now required to provide a Social Security number for each child. Suddenly, seven million children--children who had existed only as phantom exemptions on the previous year's 1040 forms--vanished, representing about one in ten of all dependent children in the United States.