It's big, it's open - but all too often it's also dumb. It's data – and councils are pouring out the stuff often with little interpretation to make it useful complains David Walker.

The commentariat, consultants, thinktanks and other neophiliacs all extol the age of data. Great claims are made. Stupendous figures are bandied about by the likes of McKinsey, who say the application of 'big data' techniques could save European public administration €300 billion a year (a figure impossible to validate, but certainly depending on the complete abandonment of data protection and privacy).