music charts

[almusic10]

how do they know how many cds singles album have been sold then there is 1000s of shops that sell cds.

[sp1814]

The Official UK Charts Company uses a sophisticated computer system that takes retail sales information from any UK store selling in excess of 100 pieces of audio or video per week (excluding garages and mail order clubs).

Over 5,800 retailers (including all the major high street chains, approximately 600 independent stores and all major internet retailers) are linked to a central computer that reads the barcodes of every item as it is sold. These contributing outlets create the 'Universe' or 'Charts panel'.

The Official Chart returning stores cover 99% of the singles market, 95% of albums and 85% of the video market. Advanced weighting methodology is used to arrive at the total number of units sold. A number of security checks to detect sales irregularities are in place to ensure the Charts are a true reflection of the UK's most popular records.

The information is collected from Sunday to Saturday and the Official Chart is finalised between the close of business on Saturday for noon the following day. The first reveal of each new Official Chart is from 4pm on Sundays on BBC Radio 1.

I got this from www.theofficialcharts.com