Amazon has hailed its third-annual Prime Day promotion as its single biggest global shopping event ever. The sales event, held earlier this week, reached $1 billion in sales, according to some estimates, surpassing year-ago sales by 60 percent and beating the company's prior Black Friday and Cyber Monday records. More members joined Prime on this year's Prime Day than on any other single day in the company's history, Amazon said, although it did not release any figures to back up that claim.