The phrase "a large demographic" is correct and can be used in written English.
It refers to a specific group or segment of the population that shares common characteristics, such as age, gender, income level, etc. Here is an example sentence: "The new product was targeted towards a large demographic of young adults aged 18-35, who are known to be early adopters of technology."
(Is that a large demographic?) A personal favourite?
Doing so would appeal to a large demographic in the region, Vallespín said, particularly those who "don't want to leave Spain but want more out of the relationship between Spain and Catalonia".
Starbucks joins international fast food chains such as McDonalds, Taco Bell, and Dunkin Donuts, who have entered India because of a large demographic of young people with rising in income levels and international exposure.
Now they have "woken up to a large demographic of the youth that's finding Bollywood crass," said Ankur, the front-man and lyricist of the indie-rock band Ghalat Family.
In fact, Facebook is an ideal tool for the promotion of donor registration, because it rapidly spreads information to a large demographic and exerts persuasive power over its users.
One of the biggest issues will be how to invigorate Arab economies and create jobs in the face of a large demographic bulge of unemployed young people and continuing instability.
Seventeen appeals to a larger demographic, or it will when she's done retrofitting it; she calls its readers Caitlin.
It has therefore enjoyed a larger "demographic dividend" (extra growth as a result of the high ratio of workers to dependents) than its neighbours.
The Academy members certainly appear to be making an effort to move with the times and reach out to a larger demographic.
As a publication that has already seen strong growth in environmental readership, the Guardian expects this new content will expand its ability to reach a larger demographic of readers, including those who haven't previously engaged with the topic.
This is a pretty major update to the way that Twitter works and is fundamental to getting a larger demographic on a social network that can be pretty scary and unfamiliar at first.
