This figure is taken from a December 2002 BBC report: "Mobile phone firms are being overwhelmed by police requests for information about suspects' calls, the companies have complained. Almost half a million inquiries are made to the firms every year by police and customs officers, the BBC has learned".
BCSL have no more recent figure. In September 2005 we were told that:
It is clear how the location and timing data assists criminal and terrorist investigations and investigations conducted by customs and excise officers.
It should be noted that location-detection is not just a matter of crime and terrorism, there are several other applications for timing and location data. Managing traffic-flow, for example, and monitoring people's health. Keeping tabs on your children and finding your friends. The technology comes into its own whenever people are lost and was particularly valuable in the aftermath of the 2004 tsunami. Many applications are being developed by the private sector and people are pleased to subscribe to the associated services voluntarily.
There are US and EU initiatives, specifying the minimum accuracy with which it should be possible to locate mobile phones:
There are several ways to locate mobile phones and the rival technologies are engaged in healthy competition.