SCOTTSDALE, ARIZ. — Born from 1977 to 1995, millennials are the largest generation since baby boomers with 79.8 million. Together, they have $1 trillion in spending power. By 2017, they will outspend boomers, and the spending gap between the two age groups will become exponentially greater over time as the older generation heads into retirement and the younger commands a larger presence in today’s workforce, said Curt Steinhorst, certified generational keynote speaker for the Center for Generational Kinetics, Austin, Texas.

But the numbers only tell part of the story. Mr. Steinhorst also called Gen Y “the most influential generation” because they have fundamentally changed how Americans communicate and how they have become the first group of consumers to comfortably shop for food on-line, via social media and by using an increasing array of easy-to-use mobile devices.

“The way that Gen Y buys, every single other generation is modeling their buying habits after,” he explained during the American Bakers Association’s annual convention in Scottsdale in March. “While it now makes up one-third of the market, if you understand what we’re doing, you’re going to get far more than one-third of the market.”

Conventional advertising and marketing strategies such as billboards and television advertising aren’t as effective as in the past. Rather, Mr. Steinhorst noted, communicating with them directly in person, via YouTube or through a unique, positive experience with a product provides the greatest potential for building brand loyalty.

Establishing such loyalty — while not easy — can provide huge dividends in the long run.

“Gen Y is three times more likely to refer than any other generation,” Mr. Steinhorst explained. “If we have a good experience with your brand, we’re going to show up tomorrow with seven of us in a Kia. We’ll tell our 1,500 friends on Facebook, (although) most of them we’ve never actually talked to.”