The phrase "a large decrease in the proportion" is correct and usable in written English.
You can use it when discussing statistical changes or trends, particularly in contexts involving data analysis or research findings.
Example: "The study revealed a large decrease in the proportion of participants who reported symptoms over the course of the treatment."
Alternatives: "a significant drop in the percentage" or "a substantial reduction in the ratio."
For all ten hypothetical [climate change] scenarios evaluated, major shifts in the timing of monthly runoff can be seen...The changes in the timing of runoff occur primarily because of the increase in average temperatures, which has two effects: (i) a large decrease in the proportion of winter precipitation that falls as snow, and (ii) an earlier, faster, and shorter spring snowmelt".
Since then, sentinel surveillance data has shown a large decrease in the proportion of vaccine-eligible women diagnosed with genital warts at out-patient sexual health services nationwide [ 4, 5].
Both oxidative stresses do, however, produce a large decrease in the proportion of CNS linoleate in membrane phospholipids (PC and PE), with a correspondingly large increase in the proportion in TAG.
In addition, one can observe a large decrease in proportion of keeping the habit for males after 15 to 25 years of chewing.
Ethiopia achieved the largest decrease in the proportion of the population having to defecate in the open, from 92% in 1990 to 29% in 2015.
Eritrea's neighbour Ethiopia has achieved the largest decrease in the proportion of the population practising open defecation, from 92% in 1990 to 29% in 2015.
SS had the largest decrease in the proportion of participants with IFG.
For example the remarkably large decrease in proportions of smokers in both groups suggests the influence of these factors.
In a large Swiss study [ 33], there was a 5-fold decrease in the proportion of children with elevated BP following triplicate BP measurements.
Ethiopia mobilized community workers and achieved the largest decrease globally in the proportion of the population who defecate in the open.
There was a decrease in the proportion of patients receiving antibiotics and while a large proportion of patients continued to receive bronchodilators, fewer patients received multiple bronchodilators.
