Members of Congress, state legislators, and many city council and school board members are elected from districts.  At least once per decade, the district lines are redrawn, block by block.

The way that district lines are drawn puts voters together in groups — some voters are kept together in one district and others are separated into different districts.  And in our system, whichever group has more votes within a district usually decides which representative wins.  

Justin Levitt provides an overview of the need for reform in Illinois and highlights some important components effective reform should incorporate.