The phrase "contribute a proportion" is correct and usable in written English.
You could use it when you are talking about giving a certain amount for a certain purpose. For example: "The members of the club agreed to contribute a proportion of their monthly salary to charity."
Perhaps local governments could contribute a proportion of the asking price of a house if it is to be sold to a local who will actually live in it?
I suggest that, for a start, each participating council should contribute a proportion in the order of 0.5% of its budget into a common pool.
The authority has also just announced it will continue the entire funding of the performing arts festival till 2012, after which organisers will have to contribute a proportion of the running costs.
We consider case and control samples from k genetically divergent populations, of which the ith population contributes a proportion of the cases (r i ) and a proportion of the controls (s i ).
Surely the United States can afford to contribute a larger proportion of that total.
Aviation is predicted to contribute a large proportion of future greenhouse gas emissions, but politicians have been reluctant to act, as the long-term trend for passengers and flights is a rapid rise.
Three large hotels the Ramses Hilton, the Nile Hilton, and the Semiramis Intercontinental surround the square, catering to some of the twelve million tourists who contribute a significant proportion to Egypt's economy.
And because power sellers, like all other sellers, pay eBay listing fees and commissions ranging from 1.25 to 5percentt of the value of each item sold, they contribute a huge proportion of the company's revenues.
Three large hotels — the Ramses Hilton, the Nile Hilton, and the Semiramis Intercontinental — surround the square, catering to some of the twelve million tourists who contribute a significant proportion to Egypt's economy.
