The phrase "a substantial decline of" is correct and usable in written English.
It can be used when discussing a significant decrease in quantity, quality, or value of something.
Example: "The report indicated a substantial decline of sales in the last quarter."
Alternatives: "a significant drop in" or "a considerable decrease in".
The advent of potent antiretroviral therapies (ART) a decade ago has led to a substantial decline of morbidity and mortality in HIV infected patients [1] [3].
Our results suggest that the widespread conversion of forest to urban land in small catchments has likely resulted in a substantial decline of populations of stream salamanders and could have serious effects on stream ecosystems.
"I find a signinficant link between public ownership and innovation: going public causes a substantial decline of approximately 40percentt in innovation novelty as measured by patent citations," he writes in the paper.
As automobiles became the main mode of transportation, especially after World War II, middle-class families consequently moved to suburban areas, leading to a substantial decline of public transportation facilities.
Such a substantial decline of the number of officials prosecuted for wrongdoing was read as a sign that Xi's campaign might be winding down.
One of my hopes for the New Year would be for a substantial decline of the anti-intellectual fervor that has been dominant in our public discourse since the early 1980's.
As well, the wastage of caesarean kits because of lack of supervision led to a progressive undermining of the free healthcare package and a substantial decline in quality of care.
Recent (albeit limited) Breeding Bird Survey data suggest a substantial decline in numbers of this species, perhaps owing to increased predation, indiscriminate use of pesticides leading to lowered insect numbers, or habitat loss.
The majority of learners were in grades 8, 9 and 10 with a substantial decline in number of girls and boys in grades 11 and 12 (Table 1).
I also find a substantial decline in earnings of baby boomers, who reached age 60 after 2006, in their early sixties.
Previous analyses with this data showed a substantial decline in accuracy of GEBV over generations without retraining, since the selection candidates were more distant from the animals in the training population [ 25].
