The UK's first Official Download Chart debuts on Radio 1 tonight.

The chart is based on data collected from all the key UK download services, including Apple's iTunes Music Store, OD2, Napster and others.

It aggregates data concerning music downloads only, it does not cover subscription-based services. To be eligible for inclusion,. tracks must cost at least 40 pence, and cannot be over ten minutes long. However, tracks that are unavailable in any physical format are included in the chart.

Forrester Research yesterday released new predictions for Europe's digital music market, which it now expects will be worth $4.2 billion by 2009.

In excess of 60 per cent of European downloads will come from the UK, France and Germany, with Spain and Italy accounting for an additional 20 per cent of the market. Half the downnloads in the current market are genmerated by consumers aged between 16 and 24.