Sorry, Darling, how much child benefit data is missing?

UK chancellor Alistair Darling recently admitted that discs containing personal details of families claiming child benefit had been lost

How much information can be in each record if there are 25m child benefit records on two CDs? David Baxter

A standard CD-R will hold 703MB of data -- about 737m characters -- so two discs will hold 1.474bn. That would only be 59 characters per record. However, it seems there are only 7.25m records, each record being a family with one or more children. That would provide 203 characters of data per family, which is enough to include names and dates of birth, an address and bank details.

The simplest way to put a single database on to two CDs is to zip it using an archiving program such as WinZip. This would allow password protection, and would also compress the data. Text can easily be compressed into less than half the space, allowing more data to be stored on the discs. In this case, it could provide from 300 to 400 characters per family.

And remember, with coding, many data fields take up very little space. Country of birth, for example, only needs two characters.