We’ve heard a lot about the need for nonprofits to engage millennials—the generation born between 1979 and 1990—as a way to ensure their interest, not to mention ensure the long-term survival of the Jewish community. And it’s easy to understand why.  Millennials in the U.S. are nearly 33 million strong, and stand to inherit $40 trillion in the coming decades.

But a new study finds Jewish organizations that cater to millennials while giving short shrift to the three older adult generations may do so at their own peril.