Nielsen SoundScan is an information system that tracks sales of music and music video products throughout the United States and Canada. Sales data from point-of-sale cash registers is collected weekly from over 14,000 retail, mass merchant and non-traditional (online stores, venues, etc.) outlets. Weekly data is compiled and made available every Wednesday. SoundScan is the sales source for the Billboard music charts. You can register your CD at http://www.soundscan.com/register.html