The phrase "make up a large portion" is correct and usable in written English.
You can use it when you want to convey that something is a significant part of something else. For example, "Women make up a large portion of the customer base."
The reelin-producing members of the Cajal Retzius family make up a large portion of this group (Alcantara et al. 1998; Meyer et al. 1999), and the secreted protein is thought to be crucial for the establishment of normal lamination of the cortical plate (D'Arcangelo et al. 1995; Ogawa et al. 1995; Super et al. 2000).
We should turn our attention to such motions as they remain largely below awareness but make up a large portion of our natural behaviors.
Law enforcement officials make up a large portion of the panel.
Catan GmbH is a shareholder in Mayfair, and Catan products make up a large portion of Mayfair's revenue.
Conservatives like to point out that the richest Americans' tax payments make up a large portion of total receipts.
These are, presumably, the homes of the Mexican and Asian immigrants who make up a large portion of the plant's work force.
When dealing with young voters, who don't make up a large portion of off-year electorate, the exit polls might be overstating things a bit.
In many, perhaps most, libraries, self-service machines cannot be used for borrowing videotapes or CD's, which make up a large portion of many public library collections.
Inequities in school taxes, which make up a large portion of the property tax, seemed to develop in Rockland because towns with shared school districts had revalued at different times.
WHO BUYS IN PARIS Britons and Americans still make up a large portion of foreign buyers, Ms. McCafferty said, though she is also seeing a growing number of Italians, Russians and South Americans.
WHO BUYS IN NOVA SCOTIA Vacation-home buyers make up a large portion of the coastal market, said Tony Walters, an owner-broker at Claussen Walters and Associates, a real estate company based on Nova Scotia's south shore.
