The name arises from the arrangement of rows and columns of identical cages connected together, sharing common divider walls, as in the cells of a battery. However, introduction of the European Union Council Directive 1999/74/EC which banned conventional battery cages in the EU from January 2012 for welfare reasons, means the number of eggs from battery cages in the EU states is rapidly decreasing. The EU ban was proposed when international scientists independently observed signs of distress in caged hens.