The phrase "a deciding impact on" is correct and usable in written English.
It can be used when discussing the influence or effect that something has on a particular situation or outcome.
Example: "The new policy had a deciding impact on the company's overall performance in the market."
Alternatives: "a significant effect on" or "a crucial influence on".
How voters weigh those two views will have a decided impact on the upcoming midterm elections.
Americans on the average spend as much as seven hours a day with their sets on and, most experts agree, what they see has a decided impact on their perceptions of realities beyond the box.
Beijing's new policy initiatives are having a decided impact on the China strategies of local and foreign car companies alike.
These factors together with those related to exposure methodology, epidemiological necessity, and regulatory reform can have a decided impact on the success or failure of future research aimed at identifying a suitable biomarker of exposure.
Likewise, the passage and implementation of local emission standards and the mandated use of newer fuel types may also have a decided impact on future air quality changes arising from the increased use of diesel-powered vehicles.
It's having a decided impact not only on the people of Israel or Palestine, who are most directly affected, but also upon people throughout the region who have strong feelings about the inability to resolve this very difficult set of circumstances".
Just over half of all pensioners describe themselves as being in good health and, while demand for elderly care services is rising, the BMJ article suggests the key drivers in deciding the impact on care budgets will be medical knowledge and technology.
"Whatever the judge ultimately decides, the impact on the royal family is significant, especially since there are already elements in society, politics and the media in this country who don't want to maintain the monarchy".
But in this case, no matter what the Supreme Court decides, the impact on technology—such as methods for capturing carbon dioxide from power plants—is likely to be small (see "Capturing and Storing Carbon Dioxide in One Simple Step").
"They're having a personal impact on deciding how to use the money".
