The phrase "a narrow proportion of" is correct and usable in written English.
It can be used when discussing a small or limited percentage or fraction of a whole in various contexts, such as statistics or demographics.
Example: "In the survey, a narrow proportion of respondents indicated that they preferred the new policy over the old one."
Alternatives: "a small percentage of" or "a limited fraction of".
She loved the tall, narrow proportions of the Georgian architecture, but many of the additions and design details of previous owners had to go.
Posterior intervals on nodes became narrower, as a proportion of node age, with increasing root age under all relaxed clock analyses, but this trend was clearer in MCMCTREE.
The microcosmic heterogeneity in reservoirs is dominated by a high proportion of narrow throats.
Zuk et al. (2012) have shown that narrow-sense heritability could be substantially smaller than estimates of heritability from studies of related individuals, and consequently GWAS may explain a higher proportion of narrow-sense heritability than previously thought.
In addition to exhibiting steep environmental gradients, islands host biota with sharp variations in environmental tolerance and, paradoxically, harbour a greater proportion of narrow-range endemics when compared with continents (Carlquist 1974; Caujapé-Castells et al. 2010).
The phage φCD38-2 has been reported to have a wide host range and was least frequently detected in this data set, contrasting with the other phages that have typically exhibited a narrow spectrum of infectivity, and a larger proportion of the strains harboring medium myovirus-like sequences was found (Mayer et al. 2008; Horgan et al. 2010; Sekulovic et al. 2011, 2014).
As academia becomes more and more fragmented and balkanized into more narrow niches, an increasing proportion of what academics produce is unnecessarily obscure and obtuse, and, not surprisingly, poorly written.
A couple of paces away is the entrance to the Senate, whose narrow precincts contain a large proportion of the famous men of America.
Because the terminal stems narrow, they contain a higher proportion of green tissue and associated transient starch.
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.
