The phrase "a hefty proportion" is correct and usable in written English.
It can be used when discussing a significant or large part of something, often in contexts related to statistics, surveys, or general descriptions of quantities.
Example: "A hefty proportion of the respondents indicated that they preferred online shopping over traditional retail."
Alternatives: "a large percentage" or "a significant amount".
It represents about 15% of inventories held by the aerospace division, a hefty proportion.
The generation before us bought up a hefty proportion of British property and are now either sitting on it or leasing it to us for astronomical monthly fees.
The GIB has huge potential to leverage in a hefty proportion of the private sector investment needed for the UK's low carbon economy to flourish.
And, given the alarming rise in obesity, telling fat people to eat less will alienate a hefty proportion - forgive the expression - of the electorate.
The real purpose of quantitative easing is to bring down long-term interest rates, which affect the cost of a hefty proportion of American mortgages.
As if Carmina Burana has met High School Musical, the work has been almost impossibly sanitised – the equivalent of pulling a hefty proportion of its teeth.
With large open spaces to fill, the couple chose furniture of equally large proportions, like a hefty teak slab dining table with matching benches by the Parisian artist and designer Jerome Abel Seguin.
Placing first on our overall list is St .George, Utah -- its college-educated population increased by 167% from 2000 through 2013, making for a hefty 11.1 percentage point jump in the proportion of its population that's college educated to 32.0%.
At Northwestern, black students now make up about 8.5percentt of the student population - a hefty "critical mass," as Hall likes to call it, and the highest proportion in the Big 10.
Every year, SGP's organisers give a hefty chunk of their profits back to attendees who want to create interactive "art experiences", a significant proportion of which appear to involve getting naked.
