At the national level it is easy enough, though expensive, to account for this by surveying CPOs and including them in the sample in proportion to their share of the population.

尽管昂贵，但从国家水平来看，民意调查如按CPOs在总人口中所占的比例计算，调查就会很容易。

youdao

But there are no reliable statistics at the state or local level on the share of CPOs in the population.

ECONOMIST: Political polls

CPOs are younger, less white, and poorer than the average American.

ECONOMIST: Political polls

At the national level it is easy enough, though expensive, to account for this by surveying CPOs and including them in the sample in proportion to their share of the population.

ECONOMIST: Political polls