The Indices of deprivation 2004 are measured at the Lower Layer Super Output Area level. Super Output Areas were developed by the Office for National Statistics (ONS) from the Census 2001 Output Areas. There are two levels, the lowest (which the Index is based upon) being smaller than wards and containing a minimum of 1,000 people and 400 households. The middle layer contains a minimum of 5,000 people and 2,000 households. Earlier proposals to introduce Upper Layer Super Output Areas were dropped due to lack of demand.