The population is concentrated near the coast. [=most of the population is near the coast]人口主要集中在沿海一带。

Wealth is concentrated in the cities. [=most of the wealthy people live in the cities]财富主要集中在城市。

Power was concentrated in the hands of a few rich men. [=a few rich men had most of the power]权力主要集中在少数有钱人手里。