Brent Bouchez opened Agency Five0 six years ago in New York as an advertising firm specializing in marketing to baby boomers, on the assumption that companies would need to tune their messages differently as the last of the boomers headed into their 50s.

But the firm has only just landed its first boomer-targeted marketing effort “with real spending behind it,” Bouchez said. Two years ago, he started another agency, Bouchez Page, to capture a wider range of business.

“What held us back was the very idea of 50,” he said. “We heard, ‘I can’t go to my boss and say I’m going to an agency that targets 50-plus.’”

Bouchez and other specialists in marketing to baby boomers, the more than 75 million Americans born roughly from 1946 through 1964, said companies recognized the economic value of the group but were hesitant to shift marketing budgets away from the 83 million millennials, those born from 1982 to 2000, who remain the holy grail of advertisers.

A result is what marketers call a transitional phase in which millennials and boomers will be increasingly targeted in messages that try to bridge the groups.

“Companies want to reach boomers, but they want to do it with their general advertising message, usually a message created by and for a millennial target,” Bouchez said. “No mainstream brand has spent money on a targeted creative campaign for boomers.”

Thus far, if the aging consumer is the primary target, the pharmaceutical and retirement-related financial sectors are doing the marketing.

Consequently, boomers say they feel underserved by marketing.

“We did a survey of boomer perceptions of marketing directed at them, and over 80 percent said they feel advertisers are making mistakes, either with the wrong message or the wrong offer,” said Dave Austin, managing director of Influent50, a marketing agency created by AARP last year to help companies with branding for its members.

“We’re tired of the idea that if you put a Rolling Stones song on a commercial, you’ll reach the over-50s,” he said. “It doesn’t work that way.”

Some ads that try to take a more age-inclusive approach have hit the target, marketers said, particularly the fashion industry’s campaigns that include women older than 50, a big change from its well-known obsession with youth.

Two examples are Gap’s “Dress Normal” campaign, with Anjelica Huston and various other celebrities of different ages, and L’Oréal’s Paris line, which features women of different ages, including Helen Mirren and Blake Lively.

Peter Hubbell, founder of BoomAgers, a New York-based advertising agency and marketing consultancy focused on the aging consumer, said boomers would “respect those brands that represent them faithfully while appealing to their values and ambitions at this stage of their lives.”

The superior buying power of the boomers compared with the millennials is clearly one factor forcing marketers to recalibrate their messages.

According to a 4-year-old Nielsen-BoomAger study, by 2017, nearly 50 percent of the United States adult population will be 50 and older and will control 70 percent of the country’s disposable income. Moreover, that group stands to inherit $15 trillion in the next 20 years.

In contrast, 75 percent of millennials can afford to buy only what they need, not what they want, according to a 2015 study by BoomAger and the Natural Marketing Institute. In addition, 45 percent of them are not employed and 23 percent have college debt.

“Many millennials will not enter their prime earning and spending years until 2020, and most not until 2030,” Hubbell said. “Sobering news if you put all your eggs in this basket.”

Media consumption habits are also working toward increased marketing spending to reach boomers. According to Brian Nguyen, communications strategy director at Droga5, a New York-based advertising agency, use of mobile, tablet, video and social sharing is evening out between the groups.

In addition, streaming services like Netflix and Amazon are developing content targeted to boomers.

“As media touch points increase and buying power remains strong, marketers will have more and more compelling reasons to boomerang back to boomers,” Nguyen said.

He predicted that in the next two to three years, marketers would work increasingly to blend strategies that address millennials and boomers.

“Here at Droga5, we’ve already begun to take a more age-agnostic approach,” he said, “by building campaigns on truths and insights rather than arbitrary assumptions based on generational stereotypes.”