'growing demographic' is a correct and usable phrase in written English.
Example: The growing demographic of young professionals in the area is bringing new energy and excitement to the neighborhood.
Coastal regions have long demonstrated growing demographic concentration.
"We're a growing demographic as a voting bloc and as consumers.
But increasingly small British-based companies producing and distributing food are also serving this growing demographic.
And Snapchat itself claims to welcome the growing demographic, no doubt welcoming its spending power too.
In fact, Obama's vote benefited from almost every aspect of America's growing demographic diversity.
Migrants represent a disadvantaged and growing demographic with special health risks.
Hispanics are among the fastest growing demographic sectors in Colorado and tend to vote for Democrats.
But a new generation is facing narrower horizons and a growing demographic imbalance.
"Old women are the fastest growing demographic in the world and yet you don't see them in central parts.
Women are the fastest growing demographic of entrepreneurs and more often than not they are going it alone.
Their growing demographic presence in the Southwest has translated into increased local representation and wider political aspirations.
