Increased spending from Starbucks (NASDAQ:SBUX) loyalty cards helped the company report great sales growth so far this year. In fact, the company's success with prepaid cards has been phenomenal. 

Consider these statistics:

  • Starbucks customers add $3 billion annually to their cards, a pace that rivals many banks.
  • One-third of all Starbucks transactions in the U.S. are made using prepaid cards.
  • Starbucks expects its rewards membership base to double this year, to 9 million people.

In the following video, Fool contributor Demitrios Kalogeropoulos discusses how important loyalty cards have been to Starbucks, and how prepayments have been a good indicator of sales growth in future quarters.