The Butterfield Effect is what the Wall Street Journal refers to whenever someone says crime is down, but the prison population is up named after a guy at the New York Times who never could seem to make the connection. Now there is an article in the Times today: Civilian Death Toll Falls in Baghdad but Rises Across Iraq that exhibits the same effect.
My understanding of the surge was to start in Baghdad and force Al Quaeda Iraq out of the city into areas around it so that they could be squeezed. So one would think that if Baghdad is more secure and AQI is out of the city they might attack elseswhere. Anyway the statistics are skewed because of the attacks on the sect in Northern Iraq.