"narrow increase" is correct and can be used in written English.
It is used to describe a minor or insignificant rise in a particular value. For example, you could say, "The company's profits showed a narrow increase of 2.5% compared to last year."
That is a narrow increase over last July.
But the attendance figures puncture that happy story: the number of people going to the movies was flat, after a narrow increase in 2006 and three previous years of sharp declines.
In a quarterly earnings season featuring many big box retailers reporting declines in same-store sales, Best Buy surprised Wall Street, and itself, by reporting a narrow increase Tuesday.
Access to services of general interest must be guaranteed to all EU citizens, to safeguard their fundamental rights and to narrow increasing health inequalities.
Key characteristics of vulnerable plaques include rapid plaque growth accompanied by outward vessel remodeling without increases in luminal narrowing, increased inflammation, and rapid growth of both the hypoxic central core and adventitial vasa vasorum [8].
Narrowing increased in the group treated with dorsal instrumentation.
As electric field across narrow channel increases, ionization increases and consequently there is an increase in the number of excited states (radiative states) inside the narrow channel.
The flow and mass concentrated in the narrow portion increase with the decrease of the obliquity of seepage face.
These "narrow networks" increase the chances that a doctor, therapist or clinic you'd like to use won't be subject to the annual cap.
Thus, as is depicted in Fig. 18a, the time required to break all the existing C C bonds (tcc) increases as width of narrow channel increases.
Inappropriate use of antibiotics results in a variety of adverse outcomes: narrow coverage increases the risk of therapeutic failure whereas broad coverage increases the risk of superinfection [ 3].
