当たり【あたり】

当たり means "per": it follows one unit – usually 一 and a counter, such as ひとり一人, いちにち一日, いっこ一個 – and gives how much of something falls to each one. It is spelled in kanji or in kana, あたり, with no difference in meaning.

To describe a noun, 当たり takes の. This is the form in statistics and the news.

当たり or a bare number

In ordinary talk about how often or how much you do something, the number and counter alone are enough: いちにち一日さん三じかん時間べんきょう勉強します. 当たり belongs where a rate is being calculated or compared – prices, figures, averages.

The unit in front of 当たり is a counted amount. A place or a group name does not take it: ×この地域当たりの人口 → この地域の人口.