`1` products

`-` Dẫn chứng: However, unlike other surveys, it is based on the idea that cities are similar to products in shops.

`2` year

`-` Dẫn chứng: Each year, about `10,000` people in `20` countries take part in the CBI survey, and they grade a total of 50 cities.

`3` 50

`-` Dẫn chứng: Each year, about `10,000` people in `20` countries take part in the CBI survey, and they grade a total of 50 cities.

`4` categories

`-` Dẫn chứng: There are several categories in the survey.

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