Amazon's Prime membership of over 100 million customers is not only 11% higher than Costco's membership; Amazon's retention rate is over 90%. The fight for the millennial shopping dollar is up for grabs with Amazon's platform being more convenient for an on-the-move / just-in-time shopping demographic.
Recently RetailDive reported 33% of millennials do not shop at a brick and mortar store during any given week. With $200 billion in shopping power, catering to the millennial's unique demands will be the norm for marketers for years to come.