Amex's pricey Platinum card has found its sweet spot: 30-somethings with dinner plans

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• Millennial and Gen Z cardholders were American Express' biggest consumer spenders last quarter.
• The average new customer for the company's premier Platinum card is now 33.
• CEO Stephen Squeri criticized Trump's proposed credit card cap on the company's earnings call.

Tapping an American Express card is, more and more, a young person's game.

For the first time, millennials and Gen Zers made up the biggest slice of US consumer...