The phrase "a decisive change in" is correct and usable in written English.
It can be used to describe a significant or impactful alteration in a situation, process, or condition.
Example: "The new policy led to a decisive change in the company's approach to sustainability."
Alternatives: "a significant shift in" or "a critical transformation in".
However, his personal life took a decisive change in 1960.
The years from 1909 to 1914 mark a decisive change in his poetry.
The latter half of the 1990s brought a decisive change in Creed's work.
Is it likely to mark a decisive change in Japanese politics?
The commission for racial equality last night welcomed the poll as confirming a decisive change in public opinion.
If his killing is confirmed, it could prompt a decisive change in how the United States deals with Saudi Arabia.
"What's happening with Vietnam and Japan is not in itself a decisive change but it is a symptom of other things going on in the market which are changing the supply from China to non-Chinese sources".
Crisis: the decisive moment (as in a literary plot)... an unstable or crucial time or state of affairs in which a decisive change is impending, especially one with the distinct possibility of a highly undesirable outcome: a financial crisis, the nation's energy crisis..
Some argue, in fact, that a decisive change has occurred, and that a result of the wrenching economic downturn is that we just don't care about stuff anymore.
Continuously taking relatively "safe" positions on the revolution in Egypt threatens to further nullify the credibility in progressive circles of a politician elected on a campaign of decisive "change" in US governmental policy, and a human voice to compete with the robotic chorus of corporate America.
2. a condition of instability or danger, as in social, economic, political, or international affairs, leading to a decisive change.
