"concentrated pocket" is a correct and usable phrase in written English.
It is used to describe an area that is particularly dense or concentrated with a certain thing. For example, "The downtown area is a concentrated pocket of culture and entertainment."
Most moved from one concentrated pocket of poverty to another, east of the Anacostia River.
"It's the last concentrated pocket of Guinea worm left in the world," said Kelly Crawford, who fights the disease in Sudan for the Carter Center.
A lasting misconception about the Cronulla riots is that it was gangs of racist locals who participated that the Shire was an unfortunate, concentrated pocket of racism in an otherwise happy country.
It's very obvious – to anybody who has been near a food bank, or a women's refuge, or a probation office – that "want, ignorance, squalor, disease and idleness" still exist, at disgraceful levels, and in highly concentrated pockets.
More than 75,000 live in Brooklyn, primarily in Flatbush and Flatlands but also in Canarsie, and nearly 40,000 in Queens, mainly around Cambria Heights; there are also concentrated pockets in Rockland, Suffolk, Essex and Fairfield Counties.
Because the region also has highly concentrated pockets of wealth, it takes 19 out of the top 20 spots for highest-taxed counties.
They are concentrated in pockets of California and New York and in the Washington area.
You can find child poverty concentrated in pockets of the most relatively affluent areas, from Hove to Worcester.
But in 74 of the 94 court-catchment areas, ethnic minorities, though sometimes concentrated in pockets, make up less than 10% of the population overall.
"Serious criminal behavior is so intensely concentrated in pockets of the nation that the kids who are committing crimes are usually not part of the factory layoff, they're not affected by the credit freeze or failing mortgages," said Frank Zimring, a criminologist at University of California, Berkeley.
Once found from Turkey to the eastern coast of Russia, it is now concentrated in pockets of South and East Asia, though even here it is extinct in some countries such as Pakistan and down to fewer than 50 individuals in others, including Cambodia, China, Laos and Vietnam.
