The phrase "a narrow proportion" is correct and usable in written English.
It can be used when discussing a specific, limited ratio or fraction in a particular context, such as statistics or comparisons.
Example: "In the survey, only a narrow proportion of respondents indicated that they were satisfied with the service provided."
Alternatives: "a small percentage" or "a limited ratio".
By way of example, Mr. Garrett, in an interview with The Chicago Tribune in 1992, invoked the Federal style: "I like its chaste, attenuated look — those tall, narrow proportions.
She loved the tall, narrow proportions of the Georgian architecture, but many of the additions and design details of previous owners had to go.
Working in a narrow space with the proportions of a drinking straw, the old escalators, each weighing nearly 55 tons, had to be cut into 24 separate sections and individually moved out of the entrance on three separate cranes.
For separate loci type, the proportions fluctuated within a narrow range among most species (Supplementary Table S1).
The three large rooms on the front fully exploit their Georgian proportions and have a narrow balcony that looks out on to a park and the sea beyond.
The CDF curves for African-American and white subpopulations exhibit a narrow gap, indicating that a slightly larger proportion of whites reside in blocks with lower exposure potentials.
Merged at a right angle, the rear building was darker, with smaller windows and narrower proportions.
Limitations on available water in combination with a high proportion of poor soil nutrient supply leaves a narrow margin of management alternatives for the future especially when considering the already overwhelming proportion of the most drought tolerant Scots pine.
Narrow core promoters, which initiate over a narrow range of nucleotides, constitute a very small proportion of the total promoter count (6 %).
Generally, chimps had relatively short and broad brain proportions, whereas humans had long and narrower proportions.
